2019-03-26 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by reports of passenger service units (PSUs) becoming detached from the supporting airplane structure in several Model 737 series airplanes. This AD requires modifying the PSUs and life vest panels by replacing the existing inboard lanyard and installing two new lanyards on the outboard edge of the PSUs and life vest panels; measuring the distance between the hooks of the torsion spring of the lanyard assembly; replacing discrepant lanyard assemblies; and re-identifying serviceable lanyard assemblies. We are issuing this AD to address the unsafe condition on these products.

2019-03-04 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-400 series airplanes. This AD was prompted by reports of cracking in the splice plate on the lower sill of the overwing emergency exit doors. This AD requires repetitive inspections for such cracking and applicable on-condition actions. We are issuing this AD to address the unsafe condition on these products.

2019-03-06 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by a report indicating the passenger service units (PSUs) became separated from their attachments during several survivable accident sequences. This AD requires installing lanyard assemblies on the PSU and, for certain airplanes, on the life vest panel. We are issuing this AD to address the unsafe condition on these products.

2019-03-07 - We are superseding Airworthiness Directive (AD) 2017-16-05, which applied to certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. AD 2017-16-05 required a one-time detailed visual inspection for discrepancies in the Krueger flap bullnose attachment hardware, and related investigative and corrective actions if necessary. This AD adds airplanes and an additional inspection to determine if any Krueger flap no. 1, 2, 3, or 4 has been replaced, and related investigative and corrective actions. Since this is a rotable parts issue, the applicability of this AD has been expanded beyond the airplanes listed in the related service bulletin to include all airplanes on which a Krueger flap bullnose may be installed. This AD was prompted by a report of a Krueger flap bullnose departing an airplane during taxi, which caused damage to the wing structure and thrust reverser, and a report of a missing no. 2 Krueger flap bullnose hinge bolt from an airplane that was not included in the effectivity of AD 2017-16-05. We are issuing this AD to address the unsafe condition on these products.

2019-01-03 - We are superseding Airworthiness Directive (AD) 2016-18-01, which applied to certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. AD 2016-18-01 required repetitive lubrication of the forward and aft trunnion pin assemblies of the right and left main landing gears (MLGs); repetitive inspection of these assemblies for corrosion and chrome damage, and related investigative and corrective actions if necessary; and installation of new or modified trunnion pin assembly components, which terminated the repetitive lubrication and repetitive inspections. Since we issued AD 2016-18-01, we have determined that rotable parts were not addressed in that AD, and it is therefore necessary to include all airplanes of the affected models in the applicability. This AD retains the requirements of AD 2016-18-01, adds airplanes to the applicability, and prohibits the installation of a MLG or MLG trunnion pin assembly under certain conditions. We are issuing this AD to address the unsafe condition on these products.

2019-01-06 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by a report of cracks in a certain body station (STA) frame web and doubler at fastener holes common to the stop fitting at a certain stringer. This AD requires repetitive surface high frequency eddy current (HFEC) inspections for cracking of the frame web and doubler at the stop fitting at a certain stringer, and applicable on-condition actions. We are issuing this AD to address the unsafe condition on these products.

2018-26-06 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by reports of loose, worn, or missing attachment bolts for the main landing gear (MLG) center door assemblies. This AD requires repetitive detailed inspections of the forward and aft MLG center door assembly attachments for loose, missing, damaged, or bottomed-out attachment bolts, and any wear to the retention clip assemblies as applicable; and applicable on-condition actions. This AD also provides an optional terminating action for the repetitive inspections. We are issuing this AD to address the unsafe condition on these products.

SAIB: NM-18-33 - The Boeing Company received reports from operators of Model 737 airplanes that the fuel control switches were installed with the locking feature disengaged. The fuel control switches (or engine start switches) are installed on the control stand in the flight deck and used by the pilot to supply or cutoff fuel to the engines. The fuel control switch has a locking feature to prevent inadvertent operation that could result in unintended switch movement between the fuel supply and fuel cutoff positions. In order to move the switch from one position to the other under the condition where the locking feature is engaged, it is necessary for the pilot to lift the switch up while transitioning the switch position. If the locking feature is disengaged, the switch can be moved between the two positions without lifting the switch during transition, and the switch would be exposed to the potential of inadvertent operation. Inadvertent operation of the switch could result in an unintended consequence, such as an in-flight engine shutdown.

Recommendations The FAA recommends that all owners and operators of the affected airplanes incorporate the following actions at the earliest opportunity:

Inspect the locking feature of the fuel control switch to ensure its engagement. While the airplane is on the ground, check whether the fuel control switch can be moved between the two positions without lifting up the switch. If the switch can be moved without lifting it up, the locking feature has been disengaged and the switch should be replaced at the earliest opportunity.

For Boeing Model 737-700, -700C, -800, and -900ER series airplanes and Boeing Model 737-8 and -9 airplanes delivered with a fuel control switch having P/N 766AT613-3D: Replace the fuel control switch with a switch having P/N 766AT614-3D, which includes an improved locking feature.

We request that owners and operators report any failure of the locking feature of the fuel control switch to Boeing (see contact information provided below). The report should include the date the failure occurred, the fuel control switch P/N, airplane model, airplane serial number, and airplane registration number. Under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.), the Office of Management and Budget (OMB) has approved the information collection contained in this SAIB, and assigned OMB Control Number 2120-0731.

2018-23-51 - SUMMARY: We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-8 and -9 airplanes. This emergency AD was sent previously to all known U.S. owners and operators of these airplanes. This AD requires revising certificate limitations and operating procedures of the airplane flight manual (AFM) to provide the flight crew with runaway horizontal stabilizer trim procedures to follow under certain conditions. This AD was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer. We are issuing this AD to address the unsafe condition on these products.

2018-23-09 - We are superseding Airworthiness Directive (AD) 2016-13-16, which applied to all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. AD 2016-13-16 required an inspection or records check to determine if affected horizontal stabilizers are installed, related investigative actions, and, for affected horizontal stabilizers, repetitive inspections for any crack of the horizontal stabilizer rear spar upper chord, and corrective action if necessary. This AD requires retaining the requirements of AD 2016-13-16, with revised service information that clarifies the inspection areas and serial number information of the horizontal stabilizer. This AD was prompted by reports of a manufacturing oversight, in which a supplier omitted the required protective finish on certain bushings installed in the rear spar upper chord on horizontal stabilizers, which could lead to galvanic corrosion and consequent cracking of the rear spar upper chord. We are issuing this AD to address the unsafe condition on these products.

2018-23-51 - This emergency AD was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer. This condition, if not addressed, could cause the flight crew to have difficulty controlling the airplane, and lead to excessive nose-down attitude, significant altitude loss, and possible impact with terrain.

Disengage autopilot and control airplane pitch attitude with control column and main electric trim as required. If relaxing the column causes the trim to move, set stabilizer trim switches to CUTOUT. If runaway continues, hold the stabilizer trim wheel against rotation and trim the airplane manually.

Note: The 737-8/-9 uses a Flight Control Computer command of pitch trim to improve longitudinal handling characteristics. In the event of erroneous Angle of Attack (AOA) input, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds.

In the event an uncommanded nose down stabilizer trim is experienced on the 737-8/-9, in conjunction with one or more of the indications or effects listed below, do the existing AFM Runaway Stabilizer procedure above, ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.

An erroneous AOA input can cause some or all of the following indications and effects:

Continuous or intermittent stick shaker on the affected side only.

Minimum speed bar (red and black) on the affected side only.

Increasing nose down control forces.

IAS DISAGREE alert.

ALT DISAGREE alert.

AOA DISAGREE alert (if the option is installed).

FEEL DIFF PRESS light.

Autopilot may disengage.

Inability to engage autopilot.

Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT.

2018-20-24 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by significant changes made to the airworthiness limitations (AWL) related to fuel tank ignition prevention and the nitrogen generation system. This AD requires revision of the maintenance or inspection program, as applicable, to include the latest revision of the AWLs. We are issuing this AD to address the unsafe condition on these products.

2018-19-20 - We are superseding Airworthiness Directive (AD) 2010-25-06, which applied to certain The Boeing Company Model 737-200, -300, -400, and -500 series airplanes. AD 2010-25-06 required repetitive inspections for cracking of certain fuselage frames and stub beams, and corrective actions if necessary. AD 2010-25-06 also provided for an optional repair, which terminated the repetitive inspections. For airplanes on which a certain repair was done, AD 2010-25-06 also required repetitive inspections for cracking of certain fuselage frames and stub beams, and corrective actions if necessary. This AD retains the actions required by AD 2010-25-06 and expands the inspection area. This AD was prompted by additional cracking found in areas not covered by the inspections in AD 2010-25-06. We are issuing this AD to address the unsafe condition on these products.

2018-18-13 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of cracking in certain flanges, and the adjacent web, of the wing outboard flap track at certain positions, and a determination that new inspections of certain flap track flanges and webs forward of the rear spar attachment are necessary. This AD requires an inspection to determine the part number of the wing outboard flap track assembly; repetitive inspections of each affected wing outboard flap track for discrepancies, and applicable on-condition actions; and repetitive overhaul of each wing outboard flap track. We are issuing this AD to address the unsafe condition on these products.

2018-18-03 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by several reports of cracks in a certain floor beam lower chord at door stop fitting No. 1 of the forward airstair door cutout. This AD requires repetitive inspections for any cracks and applicable on-condition actions. We are issuing this AD to address the unsafe condition on these products.

2018-17-23 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by a report indicating that during a fleet survey on a retired Model 737 airplane, cracking was found common to the number 3 windshield assembly, aft sill web. This AD requires, at certain locations, repetitive high frequency eddy current (HFEC) inspections of the number 3 windshield assembly, aft sill web; and applicable on-condition actions. We are issuing this AD to address the unsafe condition on these products.

2018-16-09 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by report indicating that cracks were found on the fuselage frame webs at stations forward and aft of the overwing emergency exits between stringer-7 (S-7) and S-8. This AD requires repetitive high frequency eddy current (HFEC) inspections for cracking of the fuselage frame webs at certain stations between S-7 and S-8 and applicable on-condition actions. We are issuing this AD to address the unsafe condition on these products.

SAIB: NM-18-18 - This Special Airworthiness Information Bulletin is to advise registered owners and operators of The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes, and Model 737-8 airplanes, with line numbers 1 through 6,640 inclusive, of the potential for the cup holder of the First Observer’s seat to be inadvertently removed. At this time, the airworthiness concern is not an unsafe condition that would warrant airworthiness directive (AD) action under Title 14 of the Code of Federal Regulations (14 CFR) part 39. Background An operator informed us about a cup holder which stuck to a cup and was inadvertently discarded with the cup. This created an open hole, exposing the P6-11 circuit breaker panel just below the cup holder (see Figure 1). The P6-11 circuit breaker panel contains some of the airplane's primary electrical power circuit breakers. Spilling liquid or dropping something metal into the open hole could result in a short circuit of primary electrical power systems during flight. Boeing has issued Service Bulletins 737-25-1790 (for Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes), and 737-25-1791 (for Model 737-8 airplanes). This service information provides procedures to secure the cup holder by adding adhesive film to the bottom of the cup holder flange. This improves the retention force to prevent unintended removal of the cup holder.

2018-12-05 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of cracks found in the rear spar web and lower chord on the left and right wings. This AD requires repetitive detailed inspections for cracking of the rear spar web and lower chord, and applicable on-condition actions. We are issuing this AD to address the unsafe condition on these products.

2018-10-12 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD requires repetitive high frequency eddy current (HFEC) and detailed inspections, as applicable, for cracking of certain aft vertical stiffeners; repetitive detailed inspections for cracking of time-limited repairs, as applicable; a one-time HFEC inspection for cracking of the keel beam upper chord inboard flanges; a one-time general visual inspection for cracking of a certain angle; and applicable on-condition actions. This AD was prompted by a report of cracks in the left-side and right-side keel beam upper chords and aft vertical stiffeners. We are issuing this AD to address the unsafe condition on these products.

2018-09-13 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports indicating additional cracking in the inspar upper skin at wing buttock line (WBL) 157 and in the skin at two holes common to the rear spar in the same area, and rear spar web cracks were also noted on both wings. Subsequent inspections revealed that the right rear spar upper chord was almost completely severed and the left rear spar upper chord was completely severed. Additional reports identified cracking in the main landing gear (MLG) beam forward support fitting. This AD requires the installation of standard-size fasteners for a certain configuration and inspections for any crack in certain locations of the rear spar. We are issuing this AD to address the unsafe condition on these products.

2018-09-08 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-200, -300, -400, and -500 series airplanes. This AD was prompted by reports of cracks in the frame web common to the stringer ties adjacent to the air-conditioning support brackets. This AD requires an inspection of the frame for any air-conditioning bracket assembly or intercostal, and, depending on the results, repetitive inspections of the frame web for cracking of certain locations, and applicable on-condition actions. We are issuing this AD to address the unsafe condition on these products.

2018-09-10 - We are adopting a new airworthiness directive (AD) for all CFM International S.A. (CFM) Model CFM56-7B engines. This AD requires initial and repetitive inspections of the concave and convex sides of the fan blade dovetail to detect cracking and replacement of any blades found cracked. This AD was prompted by a recent engine failure due to a fractured fan blade, that resulted in the engine inlet cowl disintegrating and debris penetrating the fuselage, causing a loss of pressurization, and prompting an emergency descent. We are issuing this AD to address the unsafe condition on these products.

2018-09-01 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of cracks found in the main landing gear (MLG) beam forward support fitting. This AD requires repetitive inspections for cracking of the MLG beam forward support fitting, and applicable on-condition actions. We are issuing this AD to address the unsafe condition on these products.

2018-09-51 Emergency AD - This emergency AD was prompted by a recent event in which a Boeing Model 737-700 airplane powered by CFM56-7B model engines experienced an engine failure due to a fractured fan blade, resulting in the engine inlet cowl disintegrating. Debris penetrated the fuselage causing a loss of pressurization and prompting an emergency descent. Although the airplane landed safely, there was one passenger fatality. Fan blade failure due to cracking, if not addressed, could result in an engine in-flight shutdown (IFSD), uncontained release of debris, damage to the engine, damage to the airplane, and possible airplane decompression. Inspection (1) Within 20 days after receipt of this AD, perform a one-time ultrasonic inspection (USI) of all 24 fan blade dovetail concave and convex sides to detect cracking. (2) Use the Accomplishment Instructions, paragraphs 3.A.(3)(a) through (i), of CFM Service Bulletin CFM56-7B S/B 72-1033, dated April 20, 2018, to perform the inspection required by paragraph (g)(1) of this AD.

2018-06-05 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-300 and -500 series airplanes. This AD was prompted by a report indicating that fatigue cracks were found in the lower wing skin of an airplane with winglets installed. This AD requires repetitive inspections for cracking of the lower wing skin, and repair if necessary. We are issuing this AD to address the unsafe condition on these products.

2018-04-12 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, -500 series airplanes. This AD was prompted by a report of wire damage on a fuel boost pump power cable, and a separate report of a fuel tank explosion on a similarly equipped airplane. This AD requires the installation of new shielded wire bundles and convoluted liners within fuel tank conduits, and revision of the maintenance or inspection program, as applicable, to incorporate certain airworthiness limitations (AWLs). We are issuing this AD to address the unsafe condition on these products.

2018-04-08 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that the gore web lap splices of the aft pressure bulkhead are subject to widespread fatigue damage (WFD). This AD requires repetitive inspections of the gore webs, gore web lap splices, and repair webs, as applicable, of the aft pressure bulkhead, and applicable on-condition actions. We are issuing this AD to address the unsafe condition on these products.

2018-04-06 - We are superseding Airworthiness Directive (AD) 2012-12-05, which applied to all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. AD 2012-12-05 required repetitive inspections for cracking under the stop fittings and intercostal flanges and for cracking of the intercostal web, attachment clips, stringer splice channels, frame, reinforcement angle, shear web, frame outer chord and inner chord; a one-time inspection to detect missing fasteners; repetitive inspections of the cargo barrier net fitting for cracking; repetitive inspections for cracking of the stringer S-15L aft intercostal; and repair or corrective action if necessary. For certain airplanes, this AD adds new repetitive inspections of certain areas of the frame inner chord, and applicable on-condition actions. This AD was prompted by reports of additional cracking in locations not covered by the inspections in AD 2012-12-05. We are issuing this AD to address the unsafe condition on these products.

2018-01-08 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of fatigue cracking in the frame outboard chord and in the radius of the auxiliary chord at a certain area. This AD requires inspections to detect this cracking, and corrective action if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-25-12 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of cracking in the webs of the stub beams at certain fuselage stations. These cracks are the result of fatigue caused by cyclical loading from pressurization, wing loads, and landing loads. This AD requires repetitive inspections for cracking of the webs of the stub beams at certain fuselage stations, and applicable on-condition actions. We are issuing this AD to address the unsafe condition on these products.

2017-25-10 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by a report indicating that wear of the bearing plate slider bushings could cause disconnection of certain elevator hinges, which could excite the horizontal stabilizer under certain in-flight speed/altitude conditions and lead to degradation of the structure. This AD requires repetitive inspections and checks of certain elevator hinges and related components, repetitive replacements and tests of the bearing plate, and related investigative and corrective actions, if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-24-05 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of cracking in the upper aft skin at the rear spar of the wings. This AD requires repetitive inspections for cracking of the upper aft skin of the wings, and repair if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-23-07 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of cracks found in the lower chord of the left wing rear spar. This AD requires repetitive inspections for cracking of the lower chord of the rear spar and lower aft skin and applicable on-condition actions. We are issuing this AD to address the unsafe condition on these products.

2017-23-05 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of crack indications in the right wing upper aft skin, originating from fastener holes common to the rear spar upper chord. This AD requires repetitive inspections for cracking of the wing upper aft skin, and applicable on-condition actions. We are issuing this AD to address the unsafe condition on these products.

2017-23-02 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that the fuselage crown skin panels are subject to widespread fatigue damage (WFD). This AD requires repetitive inspections, replacement, and applicable on-condition actions for certain fuselage crown skin panels. We are issuing this AD to address the unsafe condition on these products.

2017-22-04 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of skin doublers that disbonded from their skin panels. This AD requires repetitive inspections of fuselage skin panels, and applicable on-condition actions. We are issuing this AD to address the unsafe condition on these products.

2017-20-14 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by a determination that supplemental inspections are required for timely detection of fatigue cracking for certain structural significant items (SSIs). This AD requires revising the maintenance or inspection program, as applicable, to add supplemental inspections. This AD also requires inspections to detect cracks in each SSI, and repair of any cracked structure. We are issuing this AD to address the unsafe condition on these products.

2017-20-12 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, and -200C series airplanes. This AD was prompted by a report of incidents involving fatigue cracking in transport category airplanes that are approaching or have exceeded their design service objective and a structural reevaluation that was conducted by the manufacturer. This AD requires revising the maintenance or inspection program, as applicable, to add supplemental inspections. This AD also requires inspections to detect cracks in each structural significant item (SSI), and repair of any cracked structure. We are issuing this AD to address the unsafe condition on these products.

2017-19-26 - We are superseding Airworthiness Directive (AD) 2008-12-04, which applied to certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes. AD 2008-12-04 required various repetitive inspections to detect cracks along the chem-milled steps of the fuselage skin, and to detect missing or loose fasteners in the area of a certain preventive modification or repairs; replacement of the time-limited repair with a permanent repair, if applicable; and applicable corrective actions which would end certain repetitive inspections. This AD reduces the post-modification inspection compliance times, limits installation of the preventive modification to airplanes with fewer than 30,000 total flight cycles, and adds repetitive inspections for modified airplanes. This AD was prompted by an evaluation by the design approval holder (DAH) that indicated that the upper skin panel at the chem-milled step above the lap joint is subject to widespread fatigue damage (WFD) if the modification was installed after 30,000 total flight cycles. We are issuing this AD to address the unsafe condition on these products.

2017-18-16 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-700 and -700C series airplanes. This AD was prompted by a report that, for certain airplanes, the nose-up pitch trim limit and associated warning will allow the horizontal stabilizer position to be set outside acceptable limits for a mis-trimmed takeoff condition. This AD requires, depending on airplane configuration, replacing certain pitch trim light plates, relocating certain position warning horn switches, revising certain software, removing a certain placard, and doing related investigative and corrective actions if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-17-09 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by a manufacturer's review that showed that the fuel tank access door at a certain wing buttock line did not have an engineered ground path with the mating wing structure. This AD requires replacing the fuel tank access door, doing a check of the electrical bond, doing related investigative and corrective actions if necessary, and revising the maintenance or inspection program by incorporating an airworthiness limitation (AWL). We are issuing this AD to address the unsafe condition on these products.

2017-17-06 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by a report of fatigue cracking found in a certain fuselage frame common to the water tank support intercostal clip located between certain stringers. This AD requires inspections for any cracking of a certain fuselage frame, and repair if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-17-04 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by a report of cracks in the upper aft skin of the right wing at certain fastener holes along the rear spar upper chord. This AD requires repetitive inspections for cracking of the upper aft skin of the wings, and repair if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-16-05 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by a report of a Krueger flap bullnose departing an airplane during taxi, which caused damage to the wing structure and thrust reverser. This AD requires a one-time detailed visual inspection for discrepancies in the Krueger flap bullnose attachment hardware, and related investigative and corrective actions, if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-15-12 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that the lower skin at the skin lap splice lower fastener row is subject to widespread fatigue damage (WFD). This AD requires repetitive inspections for cracking in the skin lap splice at the lower fastener row, and repair if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-14-13 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by a report of an aborted takeoff because the rudder pedals were not operating correctly. Investigation revealed a protruding screw in the rudder pedal heel rest adjacent to the pedals. This AD requires a torque check of the screws in the cover assembly of the heel rest for both the Captain and the First Officer's rudder pedals, and corrective action if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-13-13 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of frame web cracking at certain locations. This AD requires repetitive inspections in certain locations of the frame web, and corrective action if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-13-01 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by a report of a crack in a certain body station (BS) frame inboard chord during supplemental structural inspection document (SSID) inspections. This AD requires repetitive detailed and high frequency eddy current (HFEC) inspections for any crack at the frame inboard chords, and repair if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-12-05 - We are superseding Airworthiness Directive (AD) 2007-26-04 for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. AD 2007-26-04 required repetitive inspections for cracking of certain fasteners, and repair if necessary; and a preventive modification, which terminated the repetitive inspections. This AD removes the mandatory modification; adds repetitive inspections of the skin for cracking, a one-time inspection for defects of the production countersunk rivets, and corrective actions if necessary; and adds an optional skin trim-out repair, which will terminate certain inspections. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that certain skin panels are subject to widespread fatigue damage (WFD). We are issuing this AD to address the unsafe condition on these products.

2017-12-07 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-800, -900, and -900ER series airplanes. This AD was prompted by reports of in-flight failure of the left temperature control valve and control cabin trim air modulating valve. This AD requires replacing the left temperature control valve and control cabin trim air modulating valve. We are issuing this AD to address the unsafe condition on these products.

2017-10-07 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-400 series airplanes. This AD was prompted by an evaluation by the design approval holder (DAH), which indicates that the aft fuselage skin is subject to widespread fatigue damage (WFD), and reports of aft fuselage skin cracking. This AD requires repetitive inspections to detect cracking of the aft fuselage skin, inspections to detect missing or loose fasteners and any disbonding or cracking of bonded doublers, permanent repairs of time-limited repairs, related investigative and corrective actions if necessary, and skin panel replacement. We are issuing this AD to address the unsafe condition on these products.

2017-10-21 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that the fuselage skin is subject to widespread fatigue damage (WFD). This AD requires modification of the lap joint and repetitive inspections for cracking of the skin at critical fastener rows. We are issuing this AD to address the unsafe condition on these products.

2017-11-01 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, and -200C series airplanes. This AD is intended to complete certain mandated programs to support the airplane reaching its limit of validity (LOV) of the engineering data that support the established structural maintenance program. This AD requires various repetitive inspections for cracking of certain lugs on the rear spar and horizontal stabilizer, related investigative and corrective actions if necessary, and replacement of the center section rear spar upper chord as applicable. We are issuing this AD to address the unsafe condition on these products.

2017-10-22 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that the web lap splices in the aft pressure bulkhead are subject to widespread fatigue damage (WFD). This AD requires repetitive inspections of the web lap splices in the aft pressure bulkhead for cracking of the fastener holes, and repair if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-06-14 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by reports of cracks in the horizontal stabilizer lower skins. This AD requires inspections for cracking of the horizontal stabilizer lower skin, and corrective actions if necessary; and also provides actions that would terminate certain repetitive inspections. We are issuing this AD to address the unsafe condition on these products.

2017-06-01 - We are superseding Airworthiness Directive (AD) 2017-03-04, which applied to all The Boeing Company Model 737-500 series airplanes. AD 2017-03-04 required inspections to detect cracks in the fuselage skin panels, permanent repairs of time-limited repairs, skin panel replacement, and related investigative and corrective actions if necessary. This AD reduces the applicability of AD 2017-03-04. This AD was prompted by a determination that airplanes were inadvertently included in the applicability of AD 2017-03-04. We are issuing this AD to address the unsafe condition on these products.

2017-04-08 - We are superseding Airworthiness Directive (AD) 2008-13-12 R1 for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. AD 2008-13-12 R1 required various repetitive inspections for cracking of a certain splice of the fuselage, and other specified and corrective actions if necessary; and provided for an optional preventive modification, which terminated the repetitive inspections. This new AD adds an inspection to determine if the existing frame repair meets all specified requirements; a modification of a certain splice, which terminates the repetitive inspections; reduces certain inspection thresholds and repetitive intervals; and adds post-repair/post-modification inspections. This AD was prompted by reports of additional fatigue cracking of a certain splice of the fuselage and one report of a severed frame, due to susceptibility to widespread fatigue damage (WFD). We are issuing this AD to address the unsafe condition on these products.

2017-04-11 - We are adopting a new airworthiness directive (AD) all The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes. This AD was prompted by reports of paint deterioration on the surface of the main landing gear (MLG) and the early onset of corrosion in the trunnion bore of the MLG outer cylinder. This AD requires identifying affected parts, repetitive external surface detailed inspections for damage of affected parts, and related investigative and corrective actions if necessary. For certain airplanes, this AD also requires a detailed inspection and bushing replacement of the trunnion bore, and related investigative and corrective actions if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-03-04 - We are superseding Airworthiness Directive (AD) 2012-16-07 for certain The Boeing Company Model 737-500 series airplanes. AD 2012-16-07 required inspections of the fuselage skin at the chem-milled steps, and repair if necessary. This new AD adds new inspections, permanent repairs of time-limited repairs, related investigative and corrective actions if necessary, and skin panel replacement. This AD was prompted by evaluation by the design approval holder (DAH) that indicates that the fuselage skin is subject to widespread fatigue damage (WFD), and reports of cracking in certain areas of the fuselage skin. We are issuing this AD to address the unsafe condition on these products.

2017-02-12 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by reports of intergranular cracks on the front spar chord lugs of the outboard horizontal stabilizer. This AD requires repetitive inspections of the front spar chord lugs and lug bores of the horizontal stabilizer, and repair if necessary. We are issuing this AD to address the unsafe condition on these products.

2017-02-02 - We are superseding Airworthiness Directive (AD) 2005-13-30, for all The Boeing Company Model 737-100, -200, and -200C series airplanes. AD 2005-13-30 required repetitive inspections to detect discrepancies of certain fuselage skin panels located just aft of the wheel well, and repair if necessary. This new AD adds new fuselage skin inspections for cracking, inspections to detect missing or loose fasteners and any disbonding or cracking of bonded doublers, permanent repairs of time-limited repairs, related investigative and corrective actions if necessary, and skin panel replacement. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that the fuselage skin is subject to widespread fatigue damage (WFD), and reports of cracks at the chem-milled steps in the fuselage skin. We are issuing this AD to address the unsafe condition on these products.

2017-02-10 - We are superseding Airworthiness Directive (AD) 2013-19-04 for certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes. AD 2013-19-04 required repetitive inspections for cracking of the skin around the fasteners common to the ends of certain bulkhead chords, and related investigative actions and corrective actions if necessary; and provided an optional terminating modification. This new AD reduces the inspection threshold and repetitive inspection intervals. This AD was prompted by a report of cracks found in the skin at fasteners of certain bulkhead chords. We are issuing this AD to address the unsafe condition on these products.

2017-02-05 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of skin cracking found at the corners of the aft entry and aft galley doorways. This AD requires repetitive inspections for cracking of the fuselage skin assembly and the bear strap at the corners of the aft entry and aft galley doorways, and repair if necessary, which terminates the repetitive inspections of the repaired areas. We are issuing this AD to address the unsafe condition on these products.

SAIB: NM-17-06 - This Special Airworthiness Information Bulletin (SAIB) advises owners and operators of certain The Boeing Company Model 737-200, -200C, -300, -400, and -500 series airplanes of a new inspection procedure for cracking in the fuselage skin panels at the chem-mill steps.

2016-23-08 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-400 series airplanes. This AD was prompted by reports of cracks in the upper chord of the overwing stub beams at body station (STA) 578 emanating from the rivet location common to the crease beam inner chord and the overwing stub beam upper chord. This AD requires repetitive inspections for cracking, and related investigative and corrective actions if necessary. We are issuing this AD to prevent the unsafe condition on these products.

2016-22-13 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that lap splices for certain stringers are subject to widespread fatigue damage (WFD). This AD requires repetitive inspections for cracking in the lower fastener row of the lap splices of certain stringers, and repair if necessary. We are issuing this AD to address the unsafe condition on these products.

2016-22-14 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by a report of wire chafing damage, which caused an electrical arc to an adjacent hydraulic tube located on the forward bulkhead of the main landing gear (MLG) wheel well, resulting in a hole in a hydraulic tube and consequent total loss of system B hydraulic fluid. This AD requires an inspection for chafing damage of wire bundles and a hydraulic tube in the right side of the MLG wheel well, and corrective action if necessary; and installation of clamps between the wire bundles and hydraulic tube. We are issuing this AD to prevent chafing damage, which could result in electrical arcing that can cause a hole in the hydraulic tube and consequent loss of hydraulic fluid, possibly resulting in a fire in the MLG wheel well.

2016-20-02 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that the aft pressure bulkhead is subject to widespread fatigue damage (WFD). This AD requires repetitive inspections of the aft pressure bulkhead web for any cracking, incorrectly drilled fastener holes, and elongated fastener holes; and related investigative and corrective actions, if necessary. We are issuing this AD to detect and correct fatigue cracking of the aft pressure bulkhead web at the ''Y''-chord, which could result in reduced structural integrity of the airplane and rapid decompression of the fuselage.

2016-20-14 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900 and -900ER series airplanes. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that certain fastener locations in the window corner surround structure are subject to widespread fatigue damage (WFD). This AD requires repetitive high frequency eddy current (HFEC) inspections for cracking in certain fastener locations in the window corner surround structure, and repair if necessary. We are issuing this AD to detect and correct fatigue cracking around certain fastener locations that could cause multiple window corner skin cracks, which could result in rapid decompression and consequent loss of structural integrity of the airplane.

2016-18-16 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by fuel system reviews conducted by the manufacturer. This AD requires installing an automatic shutoff system for the center and auxiliary tank fuel boost pumps, as applicable; installing a placard in the airplane flight deck if necessary; replacing the P5-2 fuel system module assembly; installing the ''uncommanded ON'' (UCO) protection system for the fuel boost pumps; revising the airplane flight manual (AFM) to advise the flight crew of certain operating restrictions for airplanes equipped with an automatic shutoff system; and revising the maintenance program by incorporating new airworthiness limitations for fuel tank systems to satisfy Special Federal Aviation Regulation No. 88 requirements. We are issuing this AD to prevent operation of the center and auxiliary tank fuel boost pumps with continuous low pressure, which could lead to friction sparks or overheating in the fuel pump inlet that could create a potential ignition source inside the center and auxiliary fuel tanks. These conditions, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.

2016-18-15 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that the aft pressure bulkhead is subject to widespread fatigue damage (WFD). This AD requires repetitive inspections of the aft pressure bulkhead web for any cracking, crack indications, discrepant fastener holes, and corrosion; and corrective actions if necessary. We are issuing this AD to detect and correct cracks in the aft pressure bulkhead web, which could result in an uncontrolled decompression of the fuselage.

2016-18-01 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by reports of heavy corrosion and chrome damage on the forward and aft trunnion pin assemblies of the right and left main landing gears (MLGs). This AD requires repetitive lubrication of the forward and aft trunnion pin assemblies of the right and left MLGs; repetitive inspections of these assemblies for corrosion and chrome damage, and related investigative and corrective actions if necessary; and installation of new or modified trunnion pin assembly components, which will terminate the repetitive lubrication and repetitive inspections. We are issuing this AD to detect and correct heavy corrosion and chrome damage on the forward and aft trunnion pin assemblies of the right and left MLGs, which could result in cracking of these assemblies and collapse of the MLGs.

2016-16-13 - We are superseding Airworthiness Directive (AD) 2016-13-10, for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. AD 2016-13-10 required repetitive external detailed inspections and nondestructive inspections to detect cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between station (STA) 400 and STA 460, and repair if necessary. AD 2016-13-10 also required a preventive modification of the fuselage skin at crown stringers S-1 and S-2R. This AD requires the same actions as AD 2016-13-10, and clarifies certain regulatory text. This AD was prompted by the determination that certain regulatory text in AD 2016-13-10 requires clarification. We are issuing this AD to detect and correct fatigue cracking of the fuselage skin panels at the chem-mill steps, which could result in sudden fracture and failure of the fuselage skin panels, and consequent rapid decompression of the airplane.

2016-13-16 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by reports of a manufacturing oversight, in which a supplier omitted the required protective finish on certain bushings installed in the rear spar upper chord on horizontal stabilizers, which could lead to galvanic corrosion and consequent cracking of the rear spar upper chord. This AD requires an inspection or records check to determine if affected horizontal stabilizers are installed, related investigative actions, and for affected horizontal stabilizers, repetitive inspections for any crack of the horizontal stabilizer rear spar upper chord, and corrective action if necessary. We are issuing this AD to detect and correct cracking of the rear spar upper chord, which can result in the failure of the upper chord and consequent departure of the horizontal stabilizer from the airplane, which can lead to loss of control of the airplane.

2016-13-11 - We are superseding Airworthiness Directive (AD) 2008-05-06 for certain The Boeing Company Model 737-100, -200, -300, -400, and -500 series airplanes. AD 2008-05-06 required repetitive inspections for fatigue cracking in the longitudinal floor beam web, upper chord, and lower chord located at certain body stations, and repair if necessary. This new AD requires, for certain airplanes, an inspection to determine if tapered fillers are installed, and related investigative and corrective actions if necessary. This AD was prompted by reports of cracks in the center wing box longitudinal floor beams, upper chord, and lower chord. We are issuing this AD to detect and correct fatigue cracking of the upper and lower chords and web of the longitudinal floor beams, which could result in rapid loss of cabin pressure.

2016-13-10 - We are superseding Airworthiness Directive (AD) 2012-12-04, for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. AD 2012-12-04 required repetitive external detailed inspections and nondestructive inspections to detect cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between station (STA) 400 and STA 460, and repair if necessary. This new AD requires a preventive modification of the fuselage skin at crown stringers S-1 and S-2R. This new AD also reduces the inspection threshold for certain airplanes. This AD was prompted by a determination that, for certain airplanes, the skin pockets adjacent to the Air Traffic Control (ATC) antenna are susceptible to widespread fatigue damage. We are issuing this AD to detect and correct fatigue cracking of the fuselage skin panels at the chem-mill steps, which could result in sudden fracture and failure of the fuselage skin panels, and consequent rapid decompression of the airplane.

2016-11-04 - We are superseding Airworthiness Directive (AD) 2011-23-05 for all The Boeing Company Model 737-300, -400, and -500 series airplanes. AD 2011-23-05 required repetitive inspections for cracking of the 1.04-inch nominal diameter wire penetration hole, and applicable related investigative and corrective actions. This new AD adds new inspection areas, a modification that terminates certain inspections, post-modification inspections, and repair if necessary. This AD was prompted by an evaluation by the design approval holder (DAH) that indicates the fuselage frames and frame reinforcements are subject to widespread fatigue damage (WFD). We are issuing this AD to detect and correct fatigue cracking of the fuselage frames and frame reinforcements that could result in reduced structural integrity of the airplane.

2016-10-04 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of cracked antenna support channels, skin cracking underneath the number 2 very high frequency (VHF) antenna, and cracking in the frames attached to the internal support structure. This AD requires repetitive inspections to determine the condition of the skin and the internal support structure, and follow-on actions including corrective action as necessary. We are issuing this AD to detect and correct skin cracking of the fuselage. Such cracking could result in separation of the number 2 VHF antenna from the airplane and rapid depressurization of the cabin.

2016-09-13 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by reports of fatigue cracking found at the left-side and right-side upper frames, at a certain area. This AD requires repetitive medium frequency eddy current (MFEC) inspections for cracking of the left-side and right-side upper frames, and repair (including open hole high frequency eddy current (HFEC) inspections for cracking of fastener holes) if necessary. This AD also provides an optional preventive modification, which terminates the repetitive inspections at the modified location. We are issuing this AD to detect and correct fatigue cracking of the upper frame, which can grow in size and result in a severed frame, leading to rapid decompression and consequent reduced structural integrity of the airplane.

2016-07-16 - We are superseding Airworthiness Directive (AD) 2013-26-08 for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. AD 2013-26-08 required inspecting the orientation of both sides of the coil cord connector keyways of the number 2 windows on the flight deck; re-clocking the connector keyways, if necessary; and replacing the coil cord assemblies on both number 2 windows on the flight deck. This new AD adds airplanes to the applicability. AD 2013-26-08 resulted from reports of arcing and smoke at the left number 2 window in the flight deck. This AD was prompted by a determination that additional airplanes are subject to the same identified unsafe condition. We are issuing this AD to prevent arcing, smoke, and fire in the flight deck, which could lead to injuries to or incapacitation of the flightcrew.

2016-06-04 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by reports of cracking at certain fastener locations in the window corners of the window belt area. This AD requires repetitive high frequency eddy current (HFEC) inspections for fatigue cracking in certain fastener locations in the window corners of the window belt area, and related investigative and corrective actions if necessary. This AD also provides an optional preventive modification that terminates the inspections at the modified location. We are issuing this AD to detect and correct fatigue cracking around fastener locations that could cause multiple window corner skin cracks, which could result in rapid decompression and loss of structural integrity of the airplane.

2016-06-02 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD requires repetitive inspections for cracking in the horizontal and vertical flanges of the rear spar upper chord of the horizontal stabilizer, and related investigative and corrective actions if necessary. This AD was prompted by a report of cracking in the center section of the horizontal stabilizer. We are issuing this AD to detect and correct cracking of the rear spar center section of the horizontal stabilizer that could lead to departure of the horizontal stabilizer from the airplane.

2016-04-20 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes, Model 757 airplanes, Model 767 airplanes, and Model 777 airplanes. This AD results from fuel system reviews conducted by the manufacturer. This AD requires an inspection to determine if certain motor-operated valve (MOV) actuators for the fuel valves are installed, and replacement of any affected actuators. Previous ADs addressed this Special Federal Aviation Regulation No. 88 (SFAR 88) issue for the majority of the airplanes delivered with these actuators. Since those ADs did not cover all of the airplanes, and for some airplanes delivered with improved actuators, there was no restriction on installation of replacement actuators with the unsafe condition, this additional rulemaking action is required. As with the related ADs, we are issuing this AD to prevent electrical energy from lightning, hot shorts, or fault current from entering the fuel tank through the fuel valve actuator shaft, which could result in fuel tank explosions and consequent loss of the airplane.

2016-04-06 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by a determination that a repetitive test is needed to inspect the components on airplanes equipped with a certain air distribution system configuration. This AD requires doing repetitive testing for correct operation of the equipment cooling system and low pressure environmental control system, and corrective actions if necessary. This AD also requires, for certain airplanes, installing new relays and doing wiring changes to the environmental control system. We are issuing this AD to detect and correct latent failures of the equipment cooling system and low pressure environmental control system, which, in combination with a cargo fire event, could result in smoke in the flight deck and/or main cabin, and possible loss of aircraft control.

2016-03-01 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by a report of a crack of the forward leg of the left front spar lower chord and cracks on the lower wing skin at three fastener holes common to the nacelle outboard side load fitting. This AD requires repetitive inspections for cracks on the front spar lower chord, inspar skin, and wing skin, and corrective action if necessary. We are issuing this AD to detect and correct fatigue cracking of the forward leg of the front spar lower chord, inspar skin, and wing skin common to the nacelle outboard side load fitting, which could adversely affect the structural integrity of the wing.

2016-01-05 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-400 series airplanes, as modified by a certain supplemental type certificate. This AD was prompted by the discovery of a design drawing error regarding placards that identified incorrect squibs and pressure switches for certain fire extinguisher bottles. This AD requires a detailed inspection of certain cargo placards to determine if they are the correct placards and in the correct location, a detailed inspection of the harnesses to verify that they are marked and installed correctly, and corrective action if necessary. We are issuing this AD to detect and correct incorrectly installed harnesses for the cargo fire suppression system bottles, which could result in an incorrect activation sequence of the bottles, the inability to suppress a cargo fire quickly, and a possible uncontrollable fire.

2015-23-08 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100,-200,-200C,-300,-400, and -500 series airplanes. This AD was prompted by reports of cracks in fuselage frames, and a report of a missing strap that was not installed on a fuselage frame during production. This AD requires an inspection to determine if the strap adjacent to a certain stringer is installed, and repair if it is missing; repetitive inspections of the frame for cracking or a severed frame web; and related investigative and corrective actions if necessary. This AD also provides optional actions to terminate certain repetitive inspections. We are issuing this AD to detect and correct missing fuselage frame straps and frame cracking that can result in severed frames which, with multiple adjacent severed frames, or the combination of a severed frame and fuselage skin chemical mill cracks, can result in uncontrolled decompression of the airplane.

2015-21-06 - We are superseding Airworthiness Directive (AD) 2002-07-08 for certain The Boeing Company Model 737 airplanes. AD 2002-07-08 required repetitive inspections for cracking of the lower skin at the lower row of fasteners in the lap joints of the fuselage; repair of any cracking found; modification of the fuselage lap joints at certain locations, which terminated the repetitive inspections of the modified areas; and replacement of a certain preventive modification with an improved modification. This new AD adds repetitive inspections for cracking at certain window corner fastener holes, a preventive modification, and repair if necessary. This AD was prompted by the FAA's determination that certain modifications of the fuselage lap joints do not provide an adequate level of safety, and the subsequent discovery of cracks in additional fastener locations in the window belt skin panels, adjacent stringers, and window frames in locations outside the previous inspection area. We are issuing this AD to detect and correct fatigue cracking of the fuselage lap joints and window belt skin panels, which could result in reduced structural integrity and sudden decompression of the airplane.

2015-21-08 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD requires repetitive eddy current inspections for any cracking in the inspar upper skin, and related investigative and corrective actions if necessary. This AD was prompted by a report that an operator discovered a crack in a certain section of the inspar upper skin, just forward of the rear spar on the right wing. We are issuing this AD to detect and correct any cracking in the inspar upper skin and rear spar upper chord, which could result in the inability of the structure to carry limit load, or result in a fuel leak, which could prevent continued safe flight and landing.

2015-21-11 - We are superseding Airworthiness Directive (AD) 2015-16-01 for certain The Boeing Company Model airplanes. AD 2015-16-01 required incorporating design changes to improve the reliability of the cabin altitude warning system by installing a redundant cabin altitude pressure switch, replacing the aural warning module (AWM) with a new or reworked AWM, and changing certain wire bundles or connecting certain previously capped and stowed wires as necessary. For certain airplanes, AD 2015-16-01 also required prior or concurrent incorporation of related design changes by modifying the instrument panels, installing light assemblies, modifying the wire bundles, and installing a new circuit breaker, as necessary. This AD retains all actions required by AD 2015-16-01. This AD was prompted by the discovery of a typographical error in AD 2015-16-01 that referred to a nonexistent paragraph. We are issuing this AD to prevent the loss of cabin altitude warning, which could delay flightcrew recognition of a lack of cabin pressurization, and could result in incapacitation of the flightcrew due to hypoxia (a lack of oxygen in the body), and consequent loss of control of the airplane.

2015-21-10 - We are superseding Airworthiness Directive (AD) 2015-19-03 for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. AD 2015-19-03 required revising the maintenance or inspection program to include new airworthiness limitations. This AD continues to require a maintenance or inspection program revision, but with revised language. This AD was prompted by a determination that certain language in the airworthiness limitation was not accurate in AD 2015-19-03. We are issuing this AD to detect and correct latent failures of the fuel shutoff valve to the engine, which could result in the inability to shut off fuel to the engine and, in case of certain engine fires, an uncontrollable fire that could lead to wing failure.

2015-19-03 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by reports of latently failed fuel shutoff valves discovered during fuel filter replacement. This AD requires revising the maintenance or inspection program to include new airworthiness limitations. We are issuing this AD to detect and correct latent failures of the fuel shutoff valve to the engine, which could result in the inability to shut off fuel to the engine and, in case of certain engine fires, an uncontrollable fire that could lead to wing failure.

2015-16-08 - We are superseding Airworthiness Directive (AD) 2011-08-51 for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. AD 2011-08-51 required repetitive inspections of the lap joint at certain stringers along the entire length from certain body stations. This new AD expands the inspection area, requires additional inspections for cracks and open pockets, requires corrective actions if necessary, and revises the compliance times. This AD was prompted by an evaluation by the design approval holder (DAH) that has determined that the lower fastener holes in the lower skin of the fuselage lap splice are subject to widespread fatigue damage (WFD). We are issuing this AD to detect and correct fatigue cracking of the lower fastener holes in the lower skin of the fuselage lap splice, which could result in reduced structural integrity of the airplane.

2015-16-01 - We are superseding Airworthiness Directive (AD) 2012-19-11 for certain The Boeing Company Model 737 airplanes. AD 2012-19-11 required incorporating design changes to improve the reliability of the cabin altitude warning system by installing a redundant cabin altitude pressure switch, replacing the aural warning module (AWM) with a new or reworked AWM, and changing certain wire bundles or connecting certain previously capped and stowed wires as necessary. For certain airplanes, AD 2012-19-11 also required prior or concurrent incorporation of related design changes by modifying the instrument panels, installing light assemblies, modifying the wire bundles, and installing a new circuit breaker, as necessary. This AD was prompted by the report of a flightcrew not receiving an aural warning during a lack-of-cabin pressurization event. We are issuing this AD to prevent the loss of cabin altitude warning, which could delay flightcrew recognition of a lack of cabin pressurization, and could result in incapacitation of the flightcrew due to hypoxia (a lack of oxygen in the body), and consequent loss of control of the airplane.

2015-15-05 - We are superseding Airworthiness Directive (AD) 98-22-10 for certain The Boeing Company Model 737-100, -200, -200C, and -300 series airplanes. AD 98-22-10 required repetitive inspections for cracking of the aft frame and frame support structure of the forward service doorway, and repair if necessary. AD 98-22-10 also provided an optional terminating action for the repetitive inspection requirements of that AD. This new AD requires new inspections and adds airplanes to the applicability; for certain airplanes, this new AD provides an optional preventive modification, which terminates the repetitive inspections. This AD was prompted by reports of fatigue cracking of the aft frame and frame support structure of the forward service doorway around the six doorstop fittings, and a determination that inspections are needed in additional locations and that additional airplanes might be subject to the identified unsafe condition. We are issuing this AD to detect and correct fatigue cracking of the aft frame and frame support structure of the forward service doorway around the six doorstop fittings, which could result in door deflection and loss of pressurization.

2015-13-05 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of fatigue cracks found in the upper corners of the forward entry door skin cutout. This AD requires repetitive inspections for cracking in the upper corners of the forward entry door skin cutout, and repair if necessary. Accomplishment of this repair or a preventive modification terminates the repetitive inspections. We are issuing this AD to detect and correct cracking in the doorway upper corners, which could result in cabin depressurization.

2015-08-09 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600 and -700 series airplanes. This AD was prompted by reports of cracking in the body station (STA) 727 bulkhead lower frame. This AD requires a detailed and open hole high frequency eddy current (HFEC) inspection of the left- and right-side lower frame webs and inner chords for cracking, and corrective actions and preventative modifications if necessary. This AD also provides for optional terminating action of the repetitive inspections, under certain conditions. We are issuing this AD to detect and correct cracking in a bulkhead lower frame web and inner chord, which could result in a severed frame and induced skin cracks, and could lead to rapid decompression of the fuselage.

2015-06-07 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, 737-200, 737-200C, 737-300, 737-400, and 737-500 series airplanes. This AD was prompted by reports of cracking in the lower corners of the forward entry doorway and the upper corners of the airstairs cutout. This AD requires inspections for cracking of the forward entry doorway and airstairs cutout, and corrective actions if necessary. This AD also provides terminating action for the repetitive inspections. We are issuing this AD to detect and correct cracks in the lower corners of the forward entry door cutout and the upper corners of the airstairs cutout, which could progress and result in an inability to maintain cabin pressurization.

2015-02-26 - We are superseding Airworthiness Directive (AD) 2013-24-13 for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, -500, -600, -700, -700C, -800, and -900 series airplanes. AD 2013-24-13 required replacing the pivot link assembly for certain airplanes, replacing the seat track link assemblies or modifying the existing seat track link assembly for certain airplanes, or modifying the existing seat track link assembly fastener for certain other airplanes. AD 2013-24-13 also required inspecting, changing, or repairing the seat track link assembly for certain other airplanes. Since we issued AD 2013-24-13, a certain paragraph reference in that AD was found to be mis-identified; this AD corrects this paragraph reference. We are issuing this AD to prevent seat detachment in an emergency landing, which could cause injury to occupants of the passenger compartment and affect emergency egress.

2014-25-09 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of fatigue cracking in the skin assembly and bear strap of the aft lower corner of the forward airstair stowage doorway. This AD requires repetitive inspections for cracking of the skin assembly and bear strap of the forward airstair stowage doorway; post-repair and post-modification inspections for certain airplanes; and related investigative and corrective actions, if necessary. This AD also provides optional terminating actions for certain inspections. We are issuing this AD to detect and correct fatigue cracking, which could result in rapid loss of cabin pressure.

2014-25-03 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports from multiple operators that have found fatigue cracking in the corners of the forward galley service doorway. This AD requires repetitive inspections for any cracking of the skin and bear strap doublers in the corners of the forward galley service doorway, and corrective action if necessary. This AD also provides optional terminating actions for certain repetitive inspections. We are issuing this AD to detect and correct fatigue cracking, which could result in rapid loss of cabin pressure.

2014-23-10 - We are superseding Airworthiness Directive (AD) 2008-17-03 for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. AD 2008-17-03 required repetitive inspections to detect fuselage frame cracking, and corrective action if necessary. AD 2008-17-03 also provided for optional terminating action (repair/preventive change) for the repetitive inspections. This new AD adds airplanes to the applicability, but does not provide terminating action for the newly added airplanes. This AD was prompted by reports of cracks found at the cutout in the web of body station frame 303.9 inboard of stringer 16L, as well as a new report of cracking found on an airplane not identified in the applicability of AD 2008-17-03. We are issuing this AD to detect and correct fuselage frame cracking, which could prevent the left forward entry door from sealing correctly, and could cause in-flight decompression of the airplane.

2014-22-06 - We are superseding Airworthiness Directive (AD) 2005-07-12, which applies to certain the Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. AD 2005-07-12 required detailed and eddy current inspections to detect cracking of the frame web around the cutout for the doorstop intercostal strap at the aft side of the station (STA) 291.5 frame at stringer 16R, and corrective action if necessary. Since we issued AD 2005-07-12, we received reports of new findings of cracking at various locations of the STA 277 to STA 291.5 frames and intercostals, including webs, chords, clips, and shear ties, between stringers 7R and 17R. This new AD requires inspections for cracking at the forward galley door cutout, and corrective actions if necessary. This new AD also reduces a certain inspection threshold required by AD 2005-07-12. We are issuing this AD to detect and correct fatigue cracking of the aft frame and frame support structure of the forward galley door, which could result in a severed fuselage frame web, rapid decompression of the airplane, and possible loss of the forward galley door.

2014-20-06 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes, and Model 777 airplanes. This AD was prompted by testing reports on certain Honeywell phase 3 display units (DUs). These DUs exhibited susceptibility to radio frequency emissions in WiFi frequency bands at radiated power levels below the levels that the displays are required to tolerate for certification of WiFi system installations. The phase 3 DUs provide primary flight information including airspeed, altitude, pitch and roll attitude, heading, and navigation information to the flightcrew. This AD requires replacing the existing phase 3 DUs with phase 1, phase 2, or phase 3A DUs, and for certain replacement DUs, installing new DU database software. We are issuing this AD to prevent loss of flight-critical information displayed to the flightcrew during a critical phase of flight, such as an approach or takeoff, which could result in loss of airplane control at an altitude insufficient for recovery, or controlled flight into terrain.

2014-18-02 - We are superseding Airworthiness Directive (AD) 2014-05-02 for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. AD 2014-05-02 required repetitive inspections for cracking and corrosion of the aft pressure bulkhead, repetitive inspections of the frame chord drain path for debris, and corrective actions if necessary; and, for certain airplanes, enlargement of frame chord drain holes. This AD requires the same actions as AD 2014-05-02, but revises a certain repetitive inspection interval to avoid a misunderstanding of the repetitive inspection interval for the aft pressure bulkhead. This AD was prompted by reports from operators expressing confusion regarding a certain repetitive inspection interval for the aft pressure bulkhead. We are issuing this AD to detect and correct corrosion or cracking of the aft pressure bulkhead, which could result in loss of the aft pressure bulkhead web and stiffeners, and consequent rapid decompression of the airplane.

2014-13-10 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by a report of installation of incorrect wire support clamps within the bay area of the left and right environmental control systems (ECS) during production; the ECS bay area is a flammable fluid leakage zone. Use of incorrect wire support clamps that are not fully cushioned could allow electrical power wiring to come in contact with the exposed metal of the improper clamp, causing a short circuit and subsequent electrical arcing. This AD requires inspecting to identify the part number of the wire support clamp, and related investigative and corrective actions if necessary. We are issuing this AD to prevent electrical arcing and a potential ignition source, which, in combination with flammable fuel vapors, could result in a fuel tank explosion, and consequent loss of the airplane.

2014-13-07 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-300, -400, -500, -600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by a review of the tail strobe light installation, which revealed that the tail strobe light is not electrically bonded to primary structure of the airplane. This AD requires installing a new tail strobe light housing and a new disconnect bracket, and changing the wire bundles. This AD also requires, for certain airplanes, an inspection to determine if sealant is applied, and corrective actions if necessary. We are issuing this AD to prevent, in case of a direct lightning strike to the tail strobe light, damage to the operation of other critical airplane systems due to electromagnetic coupling and large transient voltages, and damage to the control mechanisms or surfaces due to a fire, which could result in loss of control of the airplane.

2014-12-13 - We are superseding Airworthiness Directive (AD) 2014-03-06 for all the Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. AD 2014-03-06 required repetitive inspections for cracking of the aft support fitting for the main landing gear (MLG) beam, and the rear spar upper chord and rear spar web in the area of rear spar station (RSS) 224.14; and repair if necessary. This AD clarifies two paragraph references. This AD was prompted by a determination that two paragraph references were in error. We are issuing this AD to detect and correct cracking of the aft support fitting for the main landing gear (MLG) beam, and the rear spar upper chord and rear spar web in the area of rear spar station (RSS) 224.14, which could grow and result in a fuel leak and possible fire.

2014-05-30 - We are superseding Airworthiness Directive (AD) 2013-07-07 for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. AD 2013-07-07 required inspecting to determine the part number of the attach pins of the horizontal stabilizer rear spar, and replacing certain attach pins. This new AD clarifies the parts installation limitation and prohibition, and adds a new requirement for certain airplanes on which certain attach pins were installed. This AD was prompted by inquiries from affected operators regarding the parts installation limitation and prohibition, and re-installation of certain attach pins that were removed for inspection. We are issuing this AD to prevent premature failure of the attach pins, which could cause reduced structural integrity of the horizontal stabilizer to fuselage attachment, resulting in loss of control of the airplane.

2014-03-06 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of cracks found in the aft support fitting, the rear spar upper chord, and the rear spar web. This AD requires repetitive inspections for cracking of the aft support fitting for the main landing gear (MLG) beam, and the rear spar upper chord and rear spar web in the area of rear spar station (RSS) 224.14; and repair if necessary. We are issuing this AD to detect and correct such cracks, which could grow and result in a fuel leak and possible fire.

2014-04-05 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of chaffing, arcing, and burning damage to the control cabin overhead wiring and ducting with smoke and fire caused by metal clamps installed on certain hoses. This AD requires inspecting for the presence of metal clamps, replacing metal clamps installed on the hoses to the air conditioning temperature sensor, gasper air outlet, and diffuser on the left side of the control cabin with plastic tie straps, and inspecting for and repairing damaged wire bundles. We are issuing this AD to prevent damage to wire bundles, which could cause electrical arcing that could result in a fire or smoke in the control cabin of the airplane.

2014-03-19 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -800, -900, and -900ER series airplanes modified by particular supplemental type certificates (STCs). This AD was prompted by reports of cracks found during inspections of the in-flight entertainment system radome assembly. This AD requires repetitive detailed inspections for cracks in the radome assembly, and replacement of the radome if necessary. We are issuing this AD to detect and correct cracks in the in-flight entertainment system radome assembly, which could result in the radome (or pieces) separating from the airplane and striking the tail, and consequently reducing the controllability of the airplane.

2014-01-05 - We are adopting a new airworthiness directive (AD) for certain the Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by a report of cracks in stringer splices at body station STA 360 and STA 908, between stringer (S) S-10L and S-10R; cracks in butt straps between S-5L and S-3L, and S-3R and S-5R; vertical chem-mill fuselage skin cracks at certain butt joints; and an instance of cracking that occurred in all those three structural elements on one airplane. This AD requires repetitive inspections for any cracking of stringer splices and butt straps, and related corrective and investigative actions if necessary. We are issuing this AD to detect and correct cracking in the three structural elements, which could result in the airplane not being able to sustain limit load requirements and possibly result in uncontrolled decompression.

2013-26-08 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes. This AD was prompted by reports of arcing and smoke at the left number 2 window in the flight deck. This AD requires inspecting the orientation of both sides of the coil cord connector keyways of the number 2 windows on the flight deck; re-clocking the connector keyways, if necessary; and replacing the coil cord assemblies on both number 2 windows on the flight deck. We are issuing this AD to prevent arcing, smoke, and fire in the flight deck, which could lead to injuries to or incapacitation of the flightcrew.

2013-25-05 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by fuel system reviews conducted by the manufacturer. This AD requires, depending on airplane configuration, replacing fuel pump power control relays with new relays having a ground fault interrupter (GFI) feature, installing ground studs and a bonding jumper, doing certain bonding resistance measurements, and changing the GFI relay position. This AD also requires revising the maintenance program to incorporate certain airworthiness limitations. We are issuing this AD to prevent damage to the fuel pumps caused by electrical arcing that could introduce an ignition source in the fuel tank, which, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.

2013-24-13 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, -500, -600, -700, -700C, -800, and -900 series airplanes. This AD was prompted by a report that the seat track attachment of body station 520 flexible joint is structurally deficient in resisting a 9g forward emergency load condition in certain seating configurations. This AD requires replacing the pivot link assembly on certain seats, modifying the existing seat track link assembly fastener on certain seats, or replacing the seat track link assemblies on certain seats. Also, for certain airplanes, this AD requires installing a new seat track link assembly or modifying the seat track link assembly. For certain other airplanes, this AD requires inspecting, changing, or repairing the seat track link assembly. We are issuing this AD to prevent seat detachment in an emergency landing, which could cause injury to occupants of the passenger compartment and affect emergency egress.

2013-23-04 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -800, -900, and -900ER series airplanes. This AD was prompted by reports that certain seat track bolts were found with severed head bolts due to fatigue. This AD requires replacing titanium seat track bolts with corrosion resistant steel (CRES) bolts, repetitive inspections for cracking of the splice strap and forward seat track holes, and related investigative and corrective actions if necessary. This AD also provides an optional terminating action for the repetitive inspections. We are issuing this AD to detect and correct missing or severed bolt heads, which, if not corrected, could result in the inability of the seat track to carry passenger loads, which could cause the seats to detach from the seat track, resulting in possible injury to passengers during an emergency landing or survivable crash.

2013-18-08 - We are superseding airworthiness directive (AD) 2004-18-06 for certain The Boeing Company Model 737-200, -200C, -300, -400, and -500 series airplanes. AD 2004-18-06 required repetitive inspections to find fatigue cracking of certain upper and lower skin panels of the fuselage, and follow-on and corrective actions if necessary. AD 2004-18-06 also included a terminating action for the repetitive inspections of certain modified or repaired areas only. This new AD adds new inspections for cracking of the fuselage skin along certain chem-milled lines, and corrective actions if necessary. This new AD also reduces certain thresholds and intervals required by AD 2004-18-06. This AD was prompted by new findings of vertical cracks along chem-milled steps adjacent to the butt joints. We are issuing this AD to detect and correct fatigue cracking of the skin panels, which could result in sudden fracture and failure of the skin panels of the fuselage, and consequent rapid decompression of the airplane.

2013-19-23 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by a new revision to the airworthiness limitations of the maintenance planning data (MPD) document. This AD requires revising the maintenance program to update inspection requirements to detect fatigue cracking of principal structural elements (PSEs). We are issuing this AD to detect and correct fatigue cracking of various principal structural elements (PSEs), which could adversely affect the structural integrity of these airplanes.

2013-19-08 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 727 airplanes; Model 737-100, -200, and -200C series airplanes; and Model 747-100, -100B, - 100B SUD, -200B, -200C, -200F, -300, -400, -400D, -400F, 747SR, and 747SP series airplanes. This AD was prompted by a report of an activation of the control column shaker during takeoff. This AD requires performing a general visual inspection to determine if a certain angle of attack (AOA) sensor with a paddle type vane is installed, and, for affected sensors, performing an operational test of the stall warning system, and replacing the AOA sensor with a new sensor if necessary. We are issuing this AD to prevent erroneous activation of the control column shaker during takeoff, which could result in runway overrun, failure to clear terrain or obstacles after takeoff, or reduced controllability of the airplane.

2013-19-04 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes. This AD was prompted by a report of cracks found in the skin at body station (STA) 540 just below stringer S-22L on a Model 737-700 series airplane. This AD requires repetitive detailed and high frequency eddy current inspections for cracking of the skin around the eight fasteners common to the ends of the STA 540 bulkhead chords between stringers S-22 and S-23, left and right sides; and corrective actions and preventive modification if necessary. We are issuing this AD to detect and correct fatigue cracking in the skin, which can result in rapid decompression of the cabin.

2013-19-03 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by a report of chafing damage to a wire bundle that was arcing to hydraulic tubing and caused by insufficient separation between the wire bundle and the hydraulic tubing in the main landing gear (MLG) wheel well. This AD requires an inspection for damage of wire bundles and hydraulic tubing on the right side of the forward bulkhead of the MLG wheel well; installation of new clamps; and corrective actions, as applicable. We are issuing this AD to detect and correct possible damage caused by insufficient separation between the wire bundles and hydraulic tubing to prevent electrical arcing in a flammable fluid leakage zone, which could lead to a wheel well fire.

2013-15-17 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by a report of an in-service occurrence of total loss of boost pump pressure of the fuel feed system, followed by loss of fuel system suction feed capability on one engine, and in-flight shutdown of the engine. This AD requires repetitive operational tests of the engine fuel suction feed of the fuel system, and other related testing and corrective action if necessary. We are issuing this AD to detect and correct loss of the engine fuel suction feed capability of the fuel system, which in the event of total loss of the fuel boost pumps could result in dual engine flameout, inability to restart the engines, and consequent forced landing of the airplane.

2013-15-16 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by a report of an inboard main landing gear (MLG) door assembly departure due to premature fatigue cracking in the inboard MLG door hinge fittings. This AD requires repetitive inspections for cracking of the inboard MLG door hinge fittings; and replacement or modification of cracked fittings. This AD also provides an option to remove the affected MLG door. We are issuing this AD to detect and correct fatigue cracking in the inboard MLG door hinge fittings, which could result in loss of the MLG door assembly from the airplane, and the MLG door assembly could impact the flight control surfaces and result in reduced controllability of the airplane.

2013-15-14 - We are superseding airworthiness directive (AD) 2008-06-29, which applied to all The Boeing Company Model 737-300, -400, and -500 series airplanes. AD 2008-06-29 required repetitive inspections of the downstop assemblies on the main tracks of the No. 2, 3, 4, and No. 5 slats and the inboard track of the No. 1 and 6 slats to verify if any parts are missing, damaged, or in the wrong order; other specified actions; and related investigative and corrective actions if necessary. This new AD retains these requirements and adds an inspection of the slat can interior for foreign object debris (FOD), and removal of any FOD found; modification of the slat track hardware; an inspection for FOD and for damage to the interior surface of the slat cans; and related investigative and corrective actions, if necessary. This AD was prompted by development of a modification by the manufacturer, which, when installed, would terminate the repetitive inspections. We are issuing this AD to prevent loose or missing parts in the main slat track downstop assemblies, which could puncture the slat track housing and result in a fuel leak and consequent fire.

2013-13-12 - We are superseding airworthiness directive (AD) 2000-06-13 R1, which applied to certain The Boeing Company Model 737-200, -200C, -300, and -400 series airplanes. AD 2000-06- 13 R1 required repetitively inspecting for cracking of the corners of the door frame and the cross beams of the aft cargo door, and corrective actions if necessary. AD 2000-06-13 R1 also required modifying the aft cargo door, which terminates the repetitive inspections. This new AD adds airplanes to the applicability, adds inspections and related investigative and corrective actions, revises certain inspection types, and reduces a certain compliance time for modifying the doors. This AD was prompted by reports of cracking in the forward and aft corner frames of the aft cargo door and in the lower cross beam. We are issuing this AD to prevent fatigue cracking of the corners of the door frame and the cross beams of the aft cargo door, which could result in rapid depressurization of the airplane.

2013-13-15 - We are superseding airworthiness directive (AD) 87-02-07, which applied to all The Boeing Company Model 737-100 and -200 series airplanes. AD 87-02-07 required replacement of certain underwing fuel tank access covers with stronger, fire-resistant covers. This new AD also requires inspecting fuel tank access doors to determine that impact-resistant access doors are installed in the correct locations, inspecting application of stencils and index markers of impact-resistant access doors, doing corrective actions if necessary, revising the maintenance program, and adding airplanes to the applicability. This AD was prompted by reports of standard access doors installed where impact-resistant access doors are required, and reports of impact-resistant doors without stencils. We are issuing this AD to prevent foreign object penetration of the wing tank, which could lead to a fuel leak near ignition sources (engine, hot brakes), consequently leading to a fuel-fed fire.

2013-09-08 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-300, -400, and -500 series airplanes. This AD was prompted by reports of two in-service occurrences on Model 737-400 airplanes of total loss of boost pump pressure of the fuel feed system, followed by loss of fuel system suction feed capability on one engine, and in-flight shutdown of the engine. This AD requires repetitive operational tests of the engine fuel suction feed of the fuel system, and corrective actions if necessary. We are issuing this AD to detect and correct loss of the engine fuel suction feed capability of the fuel system, which, in the event of total loss of the fuel boost pumps, could result in dual engine flameout, inability to restart the engines, and consequent forced landing of the airplane.

2013-18-13+R1 - We are revising an existing airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. That AD currently requires repetitive inspections to detect cracking in the web of the aft pressure bulkhead at body station 1016 at the aft fastener row attachment to the ''Y'' chord, various inspections for discrepancies at the aft pressure bulkhead, and related investigative and corrective actions if necessary. This new AD requires clarifying certain actions specified in the existing AD. This AD was prompted by several reports of fatigue cracks in the aft pressure bulkhead. We are issuing this AD to detect and correct such fatigue cracking, which could result in rapid decompression of the fuselage.

2013-09-02 - We are superseding two existing airworthiness directives (AD) that apply to certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. Those ADs, for certain airplanes, currently require repetitive inspections of the flap track of the wing outboard flap, and corrective actions if necessary; and eventual rework of the flap track assembly and rear spar attachments. For certain airplanes, this new AD adds repetitive inspections, scheduled overhauls, correct alignment during installation, and repetitive maintenance of the flap track, and corrective actions if necessary. This new AD also adds airplanes to the applicability. This AD was prompted by reports that the work sequence and procedures used during installation of replacement tracks could cause loose or cracked tracks. We are issuing this AD to detect and correct cracking and damage in the flap track, which could cause loss of the outboard trailing edge flap and consequent reduced controllability of the airplane.

2013-09-01 - We are superseding an existing airworthiness directive (AD) for certain The Boeing Company Model 737-200, -200C, -300, -400, and -500 series airplanes. That AD currently requires a one-time mid-frequency eddy current (MFEC) inspection, a low-frequency eddy current (LFEC) inspection, and a detailed inspection for damage or cracking of stringer S-4L and S-4R lap joints and stringer clips between body station (BS) 540 and BS 727, and follow-on inspections and repair if necessary. This new AD instead requires repetitive external eddy current inspections for cracking of certain fuselage crown lap joints, and corrective actions if necessary; internal eddy current and detailed inspections for cracking of certain fuselage crown lap joints, and repair if necessary; and detailed inspections of certain stringer clips, and replacement with new stringer clips if necessary. This AD also adds airplanes to the applicability. This AD was prompted by reports of cracking of the lap joint lower row. We are issuing this AD to detect and correct cracking of the fuselage lap joints, which could result in sudden decompression of the airplane.

2013-08-01 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by reports of damaged fire seals on the forward edge of the thrust reverser. This AD requires inspecting to detect damage to the upper fire seals on the forward edge of the thrust reverser, where the fire seal contacts the 12-o'clock engine strut, and for correct stiffness and vent holes, and doing corrective actions if necessary; and installing a bracket for the fire seal. We are issuing this AD to detect and correct damage to the fire seals, which could allow airflow into the engine fire zone and could degrade the ability to extinguish an engine fire.

2013-08-18 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900 and -900ER series airplanes. This AD was prompted by a report of leaking fuel from the wing leading edge area at the inboard end of the number 5 leading edge slat. This AD requires modifying the fluid drain path in the wing leading edge area, forward of the wing front spar, and doing all applicable related investigative and corrective actions; and installing new seal disks on the latches in the fuel shutoff valve access door. We are issuing this AD to prevent flammable fluids from accumulating in the wing leading edge, and draining inboard and onto the engine exhaust nozzle, which could result in a fire.

2013-08-16 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-700 and -700C series airplanes. This AD was prompted by reports of early fatigue cracks at chem-mill areas on the crown skin panels. This AD requires repetitive inspections for cracking of the fuselage skin at certain locations at chem-mill areas, and repair if necessary. We are issuing this AD to detect and correct fatigue cracking of the skin panel at the specified chem-mill step locations, which could result in rapid decompression of the airplane.

2013-08-15 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-800 series airplanes. This AD was prompted by reports of early fatigue cracks at chemmill areas on the crown skin panels. This AD requires repetitive inspections for cracking of the fuselage skin along chem-mill steps at certain crown skin and shear wrinkle areas, and repair if necessary. We are issuing this AD to detect and correct fatigue cracking of the skin panel at the specified chem-mill step locations, which could result in rapid decompression of the airplane.

2013-08-11 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-900 and -900ER series airplanes. This AD was prompted by reports of early fatigue cracks at chem-mill areas on the crown skin panels. This AD requires repetitive inspections for cracking of the fuselage skin along chem-mill steps at certain crown skin and shear wrinkle areas, and repair if necessary. We are issuing this AD to detect and correct fatigue cracking of the skin panel at the specified chem-mill step locations, which could result in rapid decompression of the airplane.

2013-08-08 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600 series airplanes. This AD was prompted by reports of early fatigue cracks at chemmill areas on the crown skin panels. This AD requires repetitive inspections for cracking of the fuselage skin at certain locations at chem-mill areas, and repair if necessary. We are issuing this AD to detect and correct fatigue cracking of the skin panel at the specified chem-mill step locations, which could result in rapid decompression of the airplane.

2013-06-05 - We are superseding an existing airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. That AD currently requires repetitive inspections of the aft attach lugs of the elevator tab control mechanisms, and replacement of any discrepant elevator tab control mechanism. This new AD requires replacing the left and right elevator tab control mechanisms with elevator tab control mechanisms that have the modified attach lugs, which would terminate the existing requirements. This AD was prompted by reports of failure of the aft attach lugs on the elevator tab control mechanisms, which resulted in severe elevator vibration; and reports of gaps in elevator tab control mechanisms and analysis indicating that additional elevator tab control mechanisms might have bearings that will come loose. We are issuing this AD to prevent discrepancies in the aft attach lugs of the elevator tab control mechanism, which could result in severe elevator and tab vibration. Consequent structural failure of the elevator or horizontal stabilizer could result in loss of structural integrity and aircraft control.

2013-04-05 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by reports of cracks in the skin and surrounding structure under the number 3 very high frequency (VHF) antenna on the lower external surface of the airplane at buttock line 0.0, aft of the main landing gear wheel well. This AD requires inspecting for cracking and corrosion under the number 3 VHF antenna, and corrective actions if necessary; and, for certain airplanes, replacing bonded skin panels with solid skin panels if not previously accomplished. This AD also provides an optional preventive modification (which would terminate the inspection requirements for certain airplanes). We are issuing this AD to detect and correct cracks and corrosion of the skin and surrounding structure under the number 3 VHF antenna, which could result in separation of the antenna from the airplane, and rapid depressurization of the airplane.

2013-02-07 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by reports from the manufacturer that center overhead stowage (COS) boxes could fall from their supports under forward load levels less than the 9 g forward load requirements as defined by certain regulations. This AD requires modifying COS boxes by installing new brackets, stiffeners, and hardware as needed. We are issuing this AD to prevent detachment of COS boxes at forward load levels less than 9 g during an emergency landing, which would cause injury to passengers and/or crew, and could impede subsequent rapid evacuation.

2013-02-05 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD requires, for certain airplanes, installing two warning level indicator lights on each of the P1-3 and P3-1 instrument panels in the flight compartment. This AD also requires, for certain airplanes, replacing the existing P5-16 and P5-10 panels; and, for certain airplanes, replacing the basic P5-16 panel with a high altitude landing P5-16 panel. Additionally, this AD requires revising the airplane flight manual to remove certain requirements of previous AD actions, and to advise the flightcrew of certain changes. This AD was prompted by a design change in the cabin altitude warning system that would address the identified unsafe condition. We are issuing this AD to prevent failure of the flightcrew to recognize and react to a valid cabin altitude warning horn, which could result in incapacitation of the flightcrew due to hypoxia (a lack of oxygen in the body), and consequent loss of control of the airplane.

2013-01-03 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-300, 737-400, 737-500, and 757-200 series airplanes. This AD was prompted by a report of damage caused by electrical arcing to the wires that connect seat electronics boxes (SEBs). This AD requires installing a new relay and doing certain wiring changes of the entertainment control switch. We are issuing this AD to prevent power from being supplied to passenger seats when the entertainment control switch is in the OFF position, which could cause an electrical shock hazard resulting in serious or fatal injury to maintenance personnel.

2012-26-02 - We are superseding an existing airworthiness directive (AD) for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. That AD currently requires repetitive inspections for cracking of the crown area of the fuselage skin, and corrective actions if necessary. This new AD adds repetitive inspections for cracking using different inspection methods and inspecting additional areas, and corrective actions if necessary. This new AD also requires additional repairs to previously repaired areas and repetitive inspections for loose fasteners and replacement if necessary in certain previously repaired areas. This AD also reduces certain compliance times and extends certain other compliance times. This AD was prompted by additional reports of cracking at the horizontal chem-mill steps away from the lap joints over the entire crown area, and vertical chemmill cracks adjacent to the butt joints. We are issuing this AD to detect and correct fatigue cracking of the fuselage skin, which could cause the fuselage skin to fracture and fail, and result in rapid decompression of the airplane.

2012-25-05 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by reports of escape slides failing to deploy from the forward and aft right-hand doors during scheduled maintenance slide deployments. This AD requires modifying the escape slide. Also, for certain airplanes, this AD requires modifying or replacing the Vespel piston. For certain other airplanes, this AD requires an additional modification of the escape slide. We are issuing this AD to prevent failure of an escape slide to deploy, which could result in the slide being unusable during an emergency evacuation and increased likelihood of injury to passengers or crewmembers due to the difficulty in evacuating the airplane.

2012-24-08 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by reports of flight crew failure to activate air data probe heat. This AD requires modifying the anti-icing system for the angle of attack sensor, the total air temperature, and the pitot probes. We are issuing this AD to prevent ice from forming on air data system sensors and consequent loss of or misleading airspeed indication on all airspeed indicating systems, which could lead to loss of control of the airplane.

2012-23-14 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD was prompted by a report of a crack found in the fuselage skin under the aft drain mast. This AD requires a detailed inspection for cracking and corrosion of the channel and fillers adjacent to the drain mast bolts, an inspection to determine the location of the bonding strap, a measurement of the washers under the drain mast bolts, and related investigative actions and repair if necessary. We are issuing this AD to detect and correct cracking in the fuselage skin and internal support structure, which could result in uncontrolled decompression of the airplane.

2012-23-08 - We are superseding an existing airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes. That AD currently requires replacing the drain tube assemblies and support clamps on the aft fairing of the engine struts. This new AD requires replacing the drain tube assembly of the left and right engine strut aft fairings with a new one, which includes an integral support clamp made of nickel alloy 625. This AD also adds airplanes to the applicability. This AD was prompted by a report of a broken drain tube assembly on the left engine strut at the clamp support location under the aft fairing compartment, inside the heat shield cavity of the aft fairing. There have also been reports of tube wear at this clamp location on additional airplanes. We are issuing this AD to prevent failure of the drain tube assemblies and clamps on the aft fairings of the engine struts. Such failure could allow leaked flammable fluids in the drain systems to discharge onto the heat shields of the aft fairings of the engine struts, which could result in an undetected and uncontrollable fire.

2012-23-04 - We are superseding an existing airworthiness directive (AD) for certain The Boeing Company Model 737-100 and -200 series airplanes. The existing AD currently requires various inspections for cracks in the outboard chord of the frame at body station (BS) 727 and in the outboard chord of stringer (S) 18A, and repair or replacement of cracked parts. This new AD adds airplanes to the applicability statement in the existing AD and adds inspections for cracks in the BS 727 frame outboard chords and the radius of the auxiliary chord, for certain airplanes. This new AD also removes the inspections of the outboard chord of S-18A required by the existing AD. This AD was prompted by several reports of fatigue cracking in the frame outboard chord at BS 727 and in the radius of the auxiliary chord on airplanes that were not affected by the existing AD. We are issuing this AD to detect and correct fatigue cracking of the outboard and auxiliary chords, which could result in reduced structural integrity of the outboard chord and consequent rapid decompression of the airplane.

2012-21-08 - We are superseding an existing airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes. That AD currently requires installing and testing an updated version of the operational program software (OPS) of the flight control computers (FCCs). This new AD requires an inspection for part numbers of the operational program software of the flight control computers, and corrective actions if necessary. This AD was prompted by reports of undetected erroneous output from a single radio altimeter channel, which resulted in premature autothrottle retard during approach. We are issuing this AD to detect and correct an unsafe condition associated with erroneous output from a radio altimeter channel, which could result in premature autothrottle landing flare retard and the loss of automatic speed control, and consequent loss of control of the airplane.

2012-20-01 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, and -200C series airplanes. This AD was prompted by a report of a severed upper butt strap, and cracks in the forward skin and bonded doubler, on one airplane. This AD requires repetitive inspections for cracks and a chemical spot test in the area of station (STA) 908, and related investigative and corrective actions, if necessary. For certain airplanes, this AD requires an inspection and modification. We are issuing this AD to prevent cracks at the adjacent mating skins (forward and aft), which could initiate just above stringers S-4R and S-4L; and could grow and result in a decompression event.

2012-16-07 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-500 series airplanes. This AD was prompted by reports of chem-mill step cracking on the aft lower lobe fuselage skins. This AD requires inspections of the fuselage skin at the chem-mill steps, and repair if necessary. We are issuing this AD to detect and correct cracking on the aft lower lobe fuselage skins, which could result in decompression of the airplane.

2012-13-07 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD requires inspecting parts or doing a records review to determine if certain trailing edge flap carriages are installed, doing repetitive inspections for corrosion, and flaking or missing thermal coating on suspect carriage spindles, and related investigative and corrective actions, if necessary; this AD also provides optional terminating action for the repetitive inspections. This AD was prompted by reports of corrosion found on carriage that are located on the outboard flaps. We are issuing this AD to detect and correct corrosion of the carriage spindle, which could result in a fracture; fracture of both the inboard and outboard carriage spindles, at the forward ends through the large diameters, on a single flap assembly, could adversely affect the continued safe flight and landing of the airplane.

2012-12-05 - We are superseding two existing airworthiness directives (ADs) for certain Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. The first existing AD currently requires, for certain airplanes, repetitive inspections of the Station (STA) 348.2 frame to detect cracking under the stop fittings and intercostal flanges at stringers S-14L, S-15L, and S-16L, and corrective action if necessary. The second existing AD currently requires repetitive inspections to detect cracking of the intercostal webs, attachment clips, and stringer splice channels, and corrective action if necessary. This new AD requires that the inspection for cracking under the stop fittings be done on additional airplanes; extends the repetitive interval for certain airplanes; adds a one-time inspection to detect missing fasteners; and updates or adds certain inspection and repair instructions. This new AD also requires, for certain airplanes, repetitive inspections of the cargo barrier net fitting for cracking, and repair if necessary. This new AD also adds, for certain airplanes, repetitive inspections for cracking of the stringer S-15L aft intercostal, and repair if necessary. This AD was prompted by reports of cracking of the STA 348.2 frame above the two outboard fasteners attaching the frame inner chord and door stop fittings, and in the outboard chord at stringer S-16L. We have also received reports of missing fasteners in the STA 348.2 frame inner chord. We are issuing this AD to detect and correct fatigue cracking of the intercostals on the forward and aft sides of the forward entry door cutout, which could result in loss of the forward entry door and rapid decompression of the airplane.

2012-12-04 - We are superseding an existing airworthiness directive (AD) for certain The Boeing Company Model 737-300, -400, and -500 series airplanes. That AD currently requires repetitive external detailed inspections or non-destructive inspections to detect cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between station (STA) 400 and STA 460, and repair if necessary. This new AD adds inspections for cracking in additional fuselage skin locations, and repair if necessary. This new AD also reduces the inspection thresholds and repetitive intervals for certain airplanes. This AD was prompted by reports of additional crack findings of the fuselage skin at the chem-mill steps. We are issuing this AD to detect and correct fatigue cracking of the fuselage skin panels at the chem-mill steps, which could result in sudden fracture and failure of the fuselage skin panels, and consequent rapid decompression of the airplane.

2012-09-06 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-700 series airplanes. This AD was prompted by reports that the aft seat leg fittings span the station (STA) 521.45 ''stay-out zone.'' This AD requires for certain airplanes, replacing the seat track pivot link assemblies, seat track sections, and floor panels. For certain airplanes, this AD also requires moving certain rows of passenger seats. For certain other airplanes, this AD also requires inspecting certain areas of the seat tracks for damage, and corrective actions if necessary. We are issuing this AD to prevent failure of the seat attachment structure and possible injury to passengers during an emergency landing.

2012-08-17 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes equipped with analog transient suppression devices (ATSDs) installed in accordance with Supplemental Type Certificate ST00146BO. This AD was prompted by multiple reports of corrosion on ATSDs. This AD requires revising the maintenance program to incorporate certain limitations. We are issuing this AD to detect and correct corrosion on ATSDs, which could result in the loss of high voltage transient protection (e.g., lightning protection) in the fuel tanks and consequent fuel tank explosion and loss of the airplane.

2012-05-02 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes. This AD was prompted by reports of heat damage to the inner wall of the thrust reversers, which could result in separation of adjacent components and consequent structural damage to the airplane, damage to other airplanes, and injury to people on the ground. This AD requires modifying the thrust reverser inner walls, inspecting for damage of the upper and lower inner wall insulation blankets, measuring the electrical conductivity on the aluminum upper compression pads 2 and 3 as applicable, inspecting for discrepancies of the inner wall of the thrust reverser, and corrective actions if necessary. This AD also requires, for certain airplanes, doing various concurrent actions (including replacing the inner wall blanket insulation, installing updated full-authority digital electronic control software, and modifying the thrust reverser inner wall and insulation blankets). We are issuing this AD to correct the unsafe condition on these products.

2012-02-09 - We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 737-100, -200, -200C, and -300 series airplanes. This AD was prompted by a report from the airplane manufacturer that airplanes were assembled with air distribution ducts in the environmental control system (ECS) wrapped with Boeing Material Specification (BMS) 8-39 or Aeronautical Materials Specifications (AMS) 3570 polyurethane foam insulation, a material with fire-retardant properties that deteriorate with age. This AD requires reworking certain air distribution ducts in the ECS. We are issuing this AD to prevent ignition of the BMS 8-39 or AMS 3570 polyurethane foam insulation on the duct assemblies of the ECS due to a potential electrical arc, which could start a small fire and lead to a larger fire that may spread throughout the airplane through the ECS.

2011-27-03 - We are adopting a new airworthiness directive (AD) for all Model 737 airplanes. This AD was prompted by a report of extensive corrosion of a ballscrew used in the drive mechanism of the horizontal stabilizer trim actuator (HSTA). This AD requires repetitive inspections, lubrications, and repetitive overhauls of the ball nut and ballscrew and attachment (Gimbal) fittings for the trim actuator of the horizontal stabilizer; various modification(s); and corrective actions if necessary; as applicable. We are issuing this AD to prevent an undetected failure of the primary load path for the ballscrew in the drive mechanism of the HSTA and subsequent wear and failure of the secondary load path, which could lead to loss of control of the horizontal stabilizer and consequent loss of control of the airplane.

2011-26-09 - We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD was prompted by reports of excessive in-service wear damage of the thumbnail fairing edge seal, and of the panel rub strip and skin assembly of the fan cowl. This AD requires replacement of the thumbnail fairing edge seals on both sides of the engines with Nitronic 60 stainless steel alloy seals. We are issuing this AD to prevent failure of the fire seal, which could allow a fire in the fan compartment to spread beyond the firewall and reach the flammable fluid leakage zones, resulting in an uncontrolled fire.

2011-24-12 - We are superseding an existing airworthiness directive (AD) for certain Model 737-300, -400, and -500 series airplanes. That AD currently requires repetitive external non-destructive inspections to detect cracks in the fuselage skin along the chem-mill step at stringers S-1 and S-2 right, between station (STA) 827 and STA 847, and repair if necessary. This new AD adds inspections for cracking in additional fuselage crown skin locations, and repair if necessary. This new AD also reduces the inspection thresholds for certain airplanes, extends certain repetitive inspection intervals, and adds airplanes to the applicability of the existing AD. This AD was prompted by reports of additional crack findings of the fuselage crown skin at the chem-milled steps. We are issuing this AD to detect and correct fatigue cracking of the fuselage skin panels at the chem-milled steps, which could result in sudden fracture and failure of the fuselage skin panels, and consequent rapid decompression of the airplane.

2011-23-05 - We are superseding an existing airworthiness directive (AD) for certain Model 737- 300, -400, and -500 series airplanes. That AD currently requires repetitive inspections for cracking of the 1.04-inch nominal diameter wire penetration hole, and applicable related investigative and corrective actions. This AD reduces the compliance times for those actions. This AD was prompted by reports of cracking in the frame, or in the frame and frame reinforcement, common to the 1.04- inch nominal diameter wire penetration hole intended for wire routing; and recent reports of multiple adjacent frame cracking found before the compliance time required by the existing AD. Such cracking could reduce the structural capability of the frames to sustain limit loads, and result in cracking in the fuselage skin and subsequent rapid depressurization of the airplane. We are issuing this AD to correct the unsafe condition on these products.

2011-18-10- Corrected - We are superseding an existing airworthiness directive (AD) for the products listed above. The existing AD currently requires reviewing the airplane maintenance records to determine whether an engine has been removed from the airplane since the airplane was manufactured. For airplanes on which an engine has been removed, the existing AD also requires an inspection of the aft engine mount to determine if the center link assembly is correctly installed, and follow-on actions if necessary. This new AD expands the applicability to include airplanes on which the engine has not been previously removed, and Model 737-900ER airplanes. This AD was prompted by reports indicating that operators found that the center link assembly for the aft engine mount was reversed on several airplanes that had not had an engine removed since delivery. We are issuing this AD to prevent increased structural loads on the aft engine mount, which could result in failure of the aft engine mount and consequent separation of the engine from the airplane.

2011-20-07 - We are superseding an existing airworthiness directive (AD) for the products listed above. That AD currently requires replacement of the power control relays in the P91 and P92 power distribution panels for the fuel boost and override pumps with new, improved relays having a ground fault interrupter (GFI) feature, or installation and maintenance of universal fault interrupters (UFIs) using a certain supplemental type certificate. This new AD continues to require the actions of the existing AD and also specifies which relays may be replaced by GFIs or UFIs. This AD was prompted by a need to clarify which relays may be replaced by installation of UFIs. We are issuing this AD to prevent pump housing burn-through due to electrical arcing, which could create a potential ignition source inside a fuel tank. This condition, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.

2011-18-03 - We are adopting a new airworthiness directive (AD) for the products listed above. This AD requires installation of an automatic shutoff system for the center tank fuel boost pumps, and installation of a placard in the airplane flight deck if necessary. This AD also requires revisions to the Limitations and Normal Procedures sections of the airplane flight manual to advise the flightcrew of certain operating restrictions for airplanes equipped with an automated center tank fuel pump shutoff control. This AD further requires installation of a secondary control relay for the electrical control circuit of each of the two center tank fuel boost pumps. Additionally, this AD requires a revision to the maintenance program to incorporate Airworthiness Limitation (AWL) No. 28-AWL-23. This AD also provides an option of installation and maintenance of universal fault interrupters using a certain supplemental type certificate, which terminates certain requirements of this AD. This AD was prompted by fuel system reviews conducted by the manufacturer. We are issuing this AD to prevent center tank fuel pump operation with continuous low pressure, which could lead to friction sparks or overheating in the fuel pump inlet that could create a potential ignition source inside the center fuel tank. These conditions, in combination with flammable fuel vapors, could result in a center fuel tank explosion and consequent loss of the airplane.

2011-12-13 - We are adopting a new airworthiness directive (AD) for the products listed above. This AD requires repetitive testing of the stabilizer takeoff warning switches, and corrective actions if necessary. This AD was prompted by reports that the warning horn did not sound during the takeoff warning system test of the S132 ''nose up stab takeoff warning switch.'' We are issuing this AD to detect and correct a takeoff warning system switch failure, which could reduce the ability of the flightcrew to maintain the safe flight and landing of the airplane.

2011-08-51 - This emergency AD was prompted by a report indicating that a Model 737-300 series airplane experienced a rapid decompression when the lap joint at stringer S-4L between body station (BS) 664 and BS 727 cracked and opened up. Investigation showed that the cracking was located in the lower skin at the lower row of fasteners. The airplane had accumulated 39,781 total flight cycles and 48,740 total flight hours. This condition, if not corrected, could result in an uncontrolled decompression of the airplane. Because the lap joint and tear strap spacing configuration is the same on Model 737-400 and -500 series airplanes, these airplanes may be subject to the identified unsafe condition.

2011-06-05 - The FAA is superseding an existing airworthiness directive (AD), which applies to all Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. That AD currently requires repetitive detailed inspections of the slat track downstop assemblies to verify that proper hardware is installed, one-time torquing of the nut and bolt, and corrective actions if necessary. This new AD also requires replacing the hardware of the downstop assembly with new hardware of the downstop assembly, doing a detailed inspection or a borescope inspection of the slat cans on each wing and the lower rail of the slat main tracks for debris, replacing the bolts of the aft side guide with new bolts, and removing any debris found in the slat can. This AD also removes airplanes from the applicability. This AD results from reports of parts coming off the main slat track downstop assemblies. We are issuing this AD to prevent loose or missing parts from the main slat track downstop assemblies from falling into the slat can and causing a puncture, which could result in a fuel leak and consequent fire.

2011-04-10 - The FAA is superseding an existing airworthiness directive (AD), which applies to all Model 737-300, -400, and -500 series airplanes. That AD currently requires inspecting to determine if certain carriage spindles are installed, repetitive inspections for corrosion and indications of corrosion on affected carriage spindles, and if necessary, related investigative and corrective actions. That AD also provides an optional terminating action. This new AD mandates the optional terminating action, which eliminates the need for the repetitive inspections. This AD results from reports of corrosion found on carriage spindles that are located on the outboard trailing edge flaps. We are issuing this AD to detect and correct corrosion of the carriage spindle, which could result in fracture. Fracture of both the inboard and outboard carriage spindles, in the forward ends through the large diameters, on a flap, could adversely affect the airplane's continued safe flight and landing.

2011-03-14 - We are adopting a new airworthiness directive (AD) for the products listed above. This AD requires installing two warning level indicator lights on the P2-2 center instrument panel in the flight compartment for certain airplanes. For a certain other airplane, this AD requires activating the cabin altitude warning and takeoff configuration warning lights. For all airplanes, this AD also requires revising the airplane flight manual to remove certain requirements included by previous AD actions, requires new pressure altitude limitations for certain airplanes, and advises the flightcrew of the following changes: revised emergency procedures to use when a cabin altitude warning or rapid depressurization occurs, and revised cabin pressurization procedures for normal operations. This AD was prompted by a design change in the cabin altitude warning system that would address the identified unsafe condition. We are issuing this AD to prevent failure of the flightcrew to recognize and react properly to a valid cabin altitude warning horn, which could result in incapacitation of the flightcrew due to hypoxia (lack of oxygen in body), and consequent loss of control of the airplane.

2011-01-12 - We are superseding an existing airworthiness directive (AD) for the products listed above. That AD currently requires repetitive inspections for discrepancies of the fuse pins of the inboard and outboard midspar fittings of the nacelle strut, and corrective actions if necessary. This new AD requires replacing the midspar fuse pins with new, improved fuse pins, which would terminate the repetitive inspections. This AD was prompted by a report of corrosion damage of the chrome runout on the head side found on all four midspar fuse pins of the nacelle strut. Additionally, a large portion of the chrome plate was missing from the corroded area of the shank. We are issuing this AD to prevent damage of the fuse pins of the inboard and outboard midspar fittings of the nacelle strut, which could result in reduced structural integrity of the fuse pins, and consequent loss of the strut and separation of the engine from the airplane.

2010-26-06 - We are adopting a new airworthiness directive (AD) for certain Model 737-600, -700, -700C, -800, and -900 series airplanes. This AD requires inspections for scribe lines in the fuselage skin at lap joints, the splice strap at certain butt joints, the skin or doubler at certain approved repair doublers, and the skin at decal locations; and related investigative and corrective actions if necessary. This AD results from reports of scribe line damage found adjacent to the skin lap joints, decals, and wing-to-body fairings. We are issuing this AD to detect and correct scribe lines, which can develop into fatigue cracks in the skin. Undetected fatigue cracks can grow and cause sudden decompression of the airplane.

2010-25-06 - We are adopting a new airworthiness directive (AD) for certain Model 737-200, -300, -400, and -500 series airplanes. This AD requires repetitive inspections for cracking of certain fuselage frames and stub beams, and corrective actions if necessary. This AD also provides for an optional repair, which would terminate the repetitive inspections. For airplanes on which a certain repair is done, this AD also requires repetitive inspections for cracking of certain fuselage frames and stub beams, and corrective actions if necessary. This AD results from reports of the detection of fatigue cracks at certain frame sections, in addition to stub beam cracking, caused by high flight cycle stresses from both pressurization and maneuver loads. We are issuing this AD to detect and correct fatigue cracking of certain fuselage frames and stub beams and possible severed frames, which could result in reduced structural integrity of the frames. This reduced structural integrity can increase loading in the fuselage skin, which will accelerate skin crack growth and could result in rapid decompression of the fuselage.

2010-19-03 - We are adopting a new airworthiness directive (AD) for certain Model 737-700 (IGW) series airplanes. This AD requires deactivation or modification of PATS Aircraft, LLC, auxiliary fuel tanks. This AD results from fuel system reviews conducted by the manufacturer. We are issuing this AD to prevent the potential of ignition sources inside fuel tanks, which, in combination with flammable fuel vapors, could result in fuel tank explosions and consequent loss of the airplane.

2010-17-14 - We are adopting a new airworthiness directive (AD) for certain Model 737-100 and -200 series airplanes. This AD requires repetitive inspections for cracking and damaged fasteners of certain fuselage frames and stub beams, and corrective actions if necessary. For certain airplanes, this AD also requires repetitive inspections for cracking of the inboard chord fastener hole of the frame at body station 639, stringer S-16, and corrective actions if necessary. For certain airplanes, this AD also requires an inspection to determine the edge margin of the lower chord. For airplanes with a certain short edge margin, this AD requires repetitive inspections for cracking, and corrective actions if necessary; replacing the lower chord terminates the repetitive inspections. This AD requires an eventual preventive modification. For certain airplanes, doing the modification or a repair terminates the repetitive inspections for the repaired or modified frame only. For airplanes on which the modification or repair is done at certain body stations, this AD requires repetitive inspections for cracking of certain frame webs and inner and outer chords, and corrective actions if necessary. For certain other airplanes, this AD requires a modification which includes reinforcing the body frame inner chords, replacing the stub beam upper chords and attach angles, and reinforcing the stub beam web. This AD results from reports of fatigue cracks at certain frame sections, in addition to stub beam cracking, caused by high flight cycle stresses from both pressurization and maneuver load. We are issuing this AD to detect and correct fatigue cracking of certain fuselage frames and stub beams, and possible severed frames, which could result in reduced structural integrity of the frames. This reduced structural integrity can increase loading in the fuselage skin, which will accelerate skin crack growth and result in rapid decompression of the fuselage.

2010-17-19 - The FAA is superseding an existing airworthiness directive (AD) that applies to all Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. The existing AD currently requires, for certain airplanes, a one-time detailed inspection of the inboard and outboard aft attach lugs of the left and right elevator tab control mechanisms for discrepancies, and replacement of any discrepant elevator tab control mechanism. For certain other airplanes, the existing AD requires that the inspections be done repetitively. Replacing the elevator tab control mechanism with a new Boeing-built mechanism terminates the repetitive inspections in the existing AD. This new AD requires that modified repetitive inspections be done on all airplanes, regardless of accomplishment of the terminating action specified in the existing AD. This AD results from reports of failure of the aft attach lugs on the elevator tab control mechanisms, which resulted in severe elevator vibration. This AD also results from reports of gaps in elevator tab control mechanisms and analysis that additional elevator tab control mechanisms might have bearings that will come loose. We are issuing this AD to detect and correct discrepancies in the aft attach lugs of the elevator tab control mechanism, which could result in elevator and tab vibration. Consequent structural failure of the elevator or horizontal stabilizer could result in loss of structural integrity and aircraft control.

2010-16-06 - We are adopting a new airworthiness directive (AD) for certain Model 737-300, -400, -500, -600, -700, and -800 series airplanes. This AD requires inspecting to verify the part number of the low-pressure flex-hoses of the crew oxygen system installed under the oxygen mask stowage boxes located within the flight deck, and replacing the flex-hose with a new non-conductive low-pressure flex-hose if necessary. This AD results from reports of low-pressure flex-hoses of the crew oxygen system that burned through due to inadvertent electrical current from a short circuit in the audio select panel. We are issuing this AD to prevent inadvertent electrical current, which can cause the low-pressure flex-hoses of the crew oxygen system to melt or burn, causing oxygen system leakage and smoke or fire.

2010-15-08 - The FAA is superseding an existing airworthiness directive (AD), which applies to all Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. That AD currently requires repetitive inspections to find cracks, fractures, or corrosion of each carriage spindle of the left and right outboard mid-flaps, and corrective action if necessary. That AD also currently requires repetitive gap checks of the inboard and outboard carriage of the outboard mid-flaps to detect fractured carriage spindles, and corrective actions if necessary. This new AD requires any new or serviceable carriage spindle installed per the requirements of the existing AD to meet minimum allowable diameter measurements taken at three locations. This AD also requires new repetitive inspections, measurements, and overhaul of the carriage spindles, and applicable corrective actions. In addition, this AD requires replacing any carriage spindle when it has reached its maximum life limit. This AD results from reports of fractures that resulted from stress corrosion and pitting along the length of the spindle and spindle diameter, and additional reports of corrosion on the outboard flap carriage spindles. We are issuing this AD to detect and correct cracked, corroded, or fractured carriage spindles, and to prevent severe flap asymmetry, which could result in reduced control or loss of controllability of the airplane.

2010-12-03 - The FAA is adopting a new airworthiness directive (AD) for certain CFM International, S.A. models CFM56-3 and -3B turbofan engines. This AD requires initial and repetitive inspections for damage to the fan blades. This AD results from a report of a failed fan blade with severe out-of-limit wear on the underside of the blade platform where it contacts the damper. We are issuing this AD to prevent failure of multiple fan blades, which could result in an uncontained failure of the engine and damage to the airplane.

2010-09-05 - The FAA is superseding an existing airworthiness directive (AD) that applies to all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. The existing AD currently requires doing a detailed inspection of the inboard and outboard aft attach lugs of the left and right elevator control tab mechanisms for gaps between the swage ring and the aft attach lug, and between the spacer and the aft attach lug; trying to move or rotate the spacer using hand pressure; and replacing any discrepant elevator tab control mechanism, including performing the detailed inspection on the replacement part before and after installation. For certain airplanes, this new AD adds improved repetitive inspections for discrepancies of the inboard and outboard aft attach lugs of the left and right elevator control tab mechanisms, and replacement if necessary. For certain other airplanes, this new AD adds a one-time inspection for discrepancies of the inboard and outboard aft attach lugs of the left and right elevator control tab mechanisms, and replacement if necessary. For airplanes on which the elevator control tab mechanism is replaced with a certain mechanism, this AD requires repetitive inspections for discrepancies of the elevator control tab mechanism and replacement if necessary. Replacing the elevator control tab mechanism with a new, Boeing-built mechanism terminates the repetitive inspections. This AD results from a report of failure of the aft attach lugs on the left elevator tab control mechanism, which resulted in severe elevator vibration; this event occurred on an airplane on which the existing AD had been done. We are issuing this AD to detect and correct a loose bearing in the aft lug of the elevator tab control mechanism, which could result in unwanted elevator and tab vibration. Consequent structural failure of the elevator or horizontal stabilizer could result in loss of structural integrity and aircraft control.

2010-06-51 - This document publishes in the Federal Register an amendment adopting airworthiness directive (AD) 2010-06-51 that was sent previously to all known U.S. owners and operators of The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes by individual notices. This AD requires doing a detailed inspection of the inboard and outboard aft attach lugs of the left and right elevator control tab mechanisms for gaps between the swage ring and the aft attach lug, and between the spacer and the aft attach lug; trying to move or rotate the spacer using hand pressure; and replacing any discrepant elevator tab control mechanism, including performing the detailed inspection on the replacement part before and after installation. This AD is prompted by a report of failure of the aft attach lugs on the left elevator tab control mechanism, which resulted in severe elevator vibration. We are issuing this AD to detect and correct a loose bearing in the aft lug of the elevator tab control mechanism, which could result in unwanted elevator and tab vibration. The consequent structural failure of the elevator or horizontal stabilizer could result in loss of aircraft control and structural integrity.

2020-06-51-Emergency - The FAA received a report of failure of the aft attach lugs on the left elevator tab control mechanism, which resulted in severe elevator vibration. The flightcrew diverted from the intended route and made an uneventful landing. Subsequent investigation revealed extensive damage to the elevator tab control system. Severe vibration in this attach point is suspected of allowing rapid wear of the joint, and resulted in failure of the attach lugs. This condition, if not corrected, could result in a loss of aircraft control and structural integrity.

2010-05-13 - The FAA is superseding an existing airworthiness directive (AD) that applies to all Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. That AD currently requires a onetime inspection for scribe lines and cracks in the fuselage skin at certain lap joints, butt joints, external repair doublers, and other areas; and related investigative/corrective actions if necessary. This new AD expands the area to be inspected and, for certain airplanes, requires earlier inspections for certain inspection zones. This AD results from additional detailed analysis of fuselage skin cracks adjacent to the skin lap joints on airplanes that had scribe lines. The analysis resulted in different inspection zones, thresholds and repetitive intervals, and airplane groupings. We are issuing this AD to prevent rapid decompression of the airplane due to fatigue cracks resulting from scribe lines on pressurized fuselage structure.

2010-02-04 - We are adopting a new airworthiness directive (AD) for certain Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD requires replacing the engine fuel shutoff valves for the left and right main tanks. This AD results from a report of a failed engine start, which was caused by an internally fractured engine fuel shutoff valve. We are issuing this AD to prevent the failure of the valve in the closed position, open position, or partially open position, which could result in engine fuel flow problems and possible uncontrolled fuel leak or fire.

2010-01-09 - We are adopting a new airworthiness directive (AD) for certain Model 737-300, -400, and -500 series airplanes. This AD requires repetitive external non-destructive inspections to detect cracks in the fuselage skin along the chem-mill step at stringers S-1 and S-2 right, between station (STA) 827 and STA 847, and repair if necessary. This AD results from a report of a hole in the fuselage skin common to stringer S-1 and S-2 left, between STA 827 and STA 847 on an airplane that diverted to an alternate airport due to cabin depressurization and subsequent deployment of the oxygen masks. We are issuing this AD to detect and correct fatigue cracking of the fuselage skin panels at the chem-milled steps, which could result in sudden fracture and failure of the fuselage skin panels, and consequent rapid decompression of the airplane.

2010-01-08 - We are adopting a new airworthiness directive (AD) for certain Model 737-600, -700, and -800 series airplanes. This AD requires an inspection of the free flange, vertical web, and radius between the free flange and vertical web of the lower stringers of the wing center section for drill starts, and applicable related investigative and corrective actions. This AD results from drill starts being found on the free flange of the lower stringers of the wing center section during a quality assurance inspection at the final assembly plant. We are issuing this AD to prevent cracks from propagating from drill starts in the free flange, vertical web, and radius between the free flange and vertical web of the lower stringers of the wing center section lower stringers, which could cause a loss of structural integrity of the wing center section and may result in a fuel leak.

2008-10-10 R1 - The FAA is revising an existing airworthiness directive (AD), which applies to certain Model 737-600, -700, -700C, -800, and -900 series airplanes. That AD currently requires revising the Airworthiness Limitations (AWLs) section of the Instructions for Continued Airworthiness by incorporating new limitations for fuel tank systems to satisfy Special Federal Aviation Regulation No. 88 requirements. That AD also requires an initial inspection to phase in certain repetitive AWL inspections, and repair if necessary. This AD clarifies the intended effect of the AD on spare and onairplane fuel tank system components. This AD results from a design review of the fuel tank systems. We are issuing this AD to prevent the potential for ignition sources inside fuel tanks caused by latent failures, alterations, repairs, or maintenance actions, which, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.

2009-26-03 - The FAA is adopting a new airworthiness directive (AD) for certain Boeing Model 737-300, -400, -500, -600, -700, -700C, -800, and -900, and 747-400 series airplanes; and Model 757, 767, and 777 airplanes. This AD requires modifying the static inverter by replacing resistor R170 with a new resistor and relocating the new resistor. This AD results from evaluation of the carbon resistor, which revealed a failure mode that can cause the resistor to ignite, involving adjacent capacitors as well. We are issuing this AD to prevent a standby static inverter from overheating, which could result in smoke in the flight deck and cabin and loss of the electrical standby power system.

2009-26-04 - The FAA is adopting a new airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. This AD requires repetitive lubrication of the left and right main landing gear (MLG) forward trunnion pins; and an inspection for discrepancies of the transition radius, lead-in chamfer, and cross-bolt bore of the MLG forward trunnion pins, and repair or replacement if necessary. Doing the applicable inspections and repairs/replacements, or overhauling the trunnion pins ends the repetitive lubrication requirements of this AD. For airplanes on which a certain repair is done, this AD requires repetitive inspections for discrepancies of the transition radius. This AD results from a report that the protective finishes on the forward trunnion pins for the left and right MLG might have been damaged during final assembly. We are issuing this AD to prevent cracking of the forward trunnion pin, which could result in fracture of the pin and consequent collapse of the MLG.

2009-24-07 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 600, -700, -700C, and -800 series airplanes. This AD requires repetitive lubrications of the right and left main landing gear (MLG) forward trunnion pins. This AD also requires an inspection for discrepancies of the transition radius of the MLG forward trunnion pins, and corrective actions if necessary. For certain airplanes, this AD also requires repetitive detailed inspections for discrepancies (including finish damage, corrosion, pitting, and base metal scratches) of the transition radius of the left and right MLG trunnion pins, and corrective action if necessary. Replacing or overhauling the trunnion pins terminates the actions required by this AD. This AD results from a report that the protective finishes on the forward trunnion pins for the left and right MLG might have been damaged during final assembly. We are issuing this AD to prevent stress corrosion cracking of the forward trunnion pins, which could result in fracture of the pins and consequent collapse of the MLG.

2009-23-10 - The FAA is superseding an existing airworthiness directive (AD) that applies to all Boeing Model 737-300, -400, and -500 series airplanes. The existing AD currently requires inspecting to determine if certain carriage spindles are installed, repetitive inspections for corrosion and indications of corrosion on affected carriage spindles, and if necessary, related investigative and corrective actions. The existing AD also provides optional terminating action. For certain airplanes, this new AD would reinstate the requirements of the existing AD. This AD results from the exclusion of certain carriage spindles from the requirements of the existing AD, and additional reports of corrosion found on carriage spindles that are located on the outboard trailing edge flaps. We are issuing this AD to detect and correct corrosion of the carriage spindle, which could result in fracture. Fracture of both the inboard and outboard carriage spindles, in the forward ends through the large diameters, on a flap, could adversely affect the airplane's continued safe flight and landing.

2009-21-01 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 300 and 737-400 series airplanes. This AD requires repetitive inspections to detect cracking of the aft fuselage skin, and related investigative/corrective actions if necessary. This AD results from reports of cracks in the aft fuselage skin on both sides of the airplane. We are issuing this AD to detect and correct cracking in the aft fuselage skin along the longitudinal edges of the bonded skin doubler, which could result in reduced structural integrity of the airplane.

2009-20-11 Corrected - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 300, -400, and -500 series airplanes. This AD requires revising the maintenance program to include new fuel system limitations for airplanes modified in accordance with STC ST00127BO. This AD also requires inspections and checks of the DTSDs and corrective actions, if necessary. This AD results from fuel system reviews conducted by the manufacturer. We are issuing this AD to prevent a potential of ignition sources inside fuel tanks, which, in combination with flammable fuel vapors, could result in a fuel tank fire or explosion and consequent loss of the airplane.

2009-19-02 - We are adopting a new airworthiness directive (AD) for all Boeing Model 737-600, - 700, -700C, -800, -900 and -900ER series airplanes. This AD requires repetitive testing of the rudder pedal forces or repetitive detailed inspections of the inner spring of the rudder feel and centering unit, and corrective actions if necessary. This AD also requires replacement of the spring assembly in the rudder feel and centering unit, which terminates the repetitive tests or inspections. This AD results from reports of low rudder pedal forces that were caused by a broken inner spring in the rudder feel and centering unit; a broken inner spring in conjunction with a broken outer spring would significantly reduce rudder pedal forces. We are issuing this AD to prevent reduced rudder pedal forces, which could result in increased potential for pilot-induced oscillations and reduce the ability of the flightcrew to maintain the safe flight and landing of the airplane.

2009-02-06R1 - We are revising an existing airworthiness directive (AD) that applies to certain Boeing Model 737-300, -400, and -500 series airplanes. That AD currently requires repetitive high frequency eddy current inspections for cracking of the 1.04-inch nominal diameter wire penetration hole in the frame and frame reinforcement, between stringers S-20 and S-21, on both the left and right sides of the airplane, and related investigative and corrective actions if necessary. This new AD clarifies certain compliance requirements. This AD results from reports of cracking in the frame, or in the frame and frame reinforcement, common to the 1.04-inch nominal diameter wire penetration hole intended for wire routing. We are issuing this AD to detect and correct cracking in the fuselage frames and frame reinforcements, which could reduce the structural capability of the frames to sustain limit loads, and result in cracking in the fuselage skin and subsequent rapid depressurization of the airplane.

2009-16-07 - The FAA is superseding an existing airworthiness directive (AD), which applies to certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. That AD currently requires replacing brackets that hold the P5 panel to the airplane structure, the standby compass bracket assembly, the generator drive and standby power module, and the air conditioning module, as applicable. The existing AD also currently requires, among other actions, inspecting for wire length and for damage of the connectors and the wire bundles, and doing applicable corrective actions if necessary. This new AD requires an additional operational test of the P5-14 panel. This AD results from a report of an electrical burning smell in the flight compartment. We are issuing this AD to prevent wire bundles from contacting the overhead dripshield panel and modules in the P5 overhead panel, which could result in electrical arcing and shorting of the electrical connector and consequent loss of several critical systems essential for safe flight; and to ensure proper operation of the passenger oxygen system. If an improperly functioning passenger oxygen system goes undetected, the passenger oxygen mask could fail to deploy and result in possible incapacitation of passengers during a depressurization event.

2009-16-14 - The FAA is superseding an existing airworthiness directive (AD) that applies to certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. That AD currently requires repetitive inspections of the intercostal webs, attachment clips, and stringer splice channels for cracks; and corrective action if necessary. This new AD reduces the repetitive inspection intervals from 25,000 flight cycles to 6,000 flight cycles, and expands the inspection area for Model 737-200C series airplanes to include the area aft of the forward entry door. This AD results from additional reports of fatigue cracks. We are issuing this AD to detect and correct fatigue cracking of the intercostals on the forward and aft sides of the forward entry door, which could result in loss of the forward entry door and rapid decompression of the airplane.

2009-14-04 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 100, -200, -200C, -300, -400, and -500 series airplanes. For certain airplanes, this AD requires deactivating or modifying the wiring to the outboard landing lights, until the wire bundles and electrical connectors have been replaced. For all airplanes, this AD also requires inspecting for any broken, damaged, or missing fairleads, grommets, and wires in the four electrical junction boxes of the main wheel well, and corrective actions if necessary. For certain airplanes, this AD also requires replacing certain wire bundles for the landing lights and fuel shutoff valves, and related investigative, other specified, and corrective actions if necessary. For certain airplanes, this AD also requires replacing of certain electrical connectors and backshell clamps. This AD results from reports of uncommanded engine shutdowns and burned and damaged wire bundles associated with the outboard landing lights and engine fuel shutoff valves. This AD also results from reports of damaged and missing grommets and broken and damaged fairleads in the electrical junction boxes of the main wheel well. We are issuing this AD to prevent a hot short between the outboard landing light and fuel shutoff valve circuits, which could result in an uncommanded engine shutdown. We are also issuing this AD to prevent corrosion of the electrical connectors of the wing rear spars, which could result in short circuits and consequent incorrect functioning of airplane systems needed for safe flight and landing.

2009-12-06 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 300, -400, -500, -600, -700, -700C, -800, and -900 series airplanes. This AD requires installing a new circuit breaker, relays, and wiring to allow the flightcrew to turn off electrical power to the in-flight entertainment (IFE) systems and other non-essential electrical systems through a switch in the flight compartment, and doing other specified actions. This AD results from an IFE systems review. We are issuing this AD to ensure that the flightcrew is able to turn off electrical power to IFE systems and other non-essential electrical systems through a switch in the flight compartment. The flightcrew's inability to turn off power to IFE systems and other non-essential electrical systems during a nonnormal or emergency situation could result in the inability to control smoke or fumes in the airplane flight deck or cabin.

2009-12-05 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 300, -400, and -500 series airplanes. This AD requires modifying the control power wiring of the normal supply fan and the low flow sensor for the equipment cooling system of the electronic flight instrument system (EFIS). This AD results from a report of loss of both the normal EFIS cooling supply and the indication of EFIS cooling loss due to a single failure of the battery bus, causing eventual power-down of the EFIS displays; the standby attitude indication is also powered by this battery bus. We are issuing this AD to prevent loss of all attitude indications from both the standby indicator and EFIS displays, which could decrease the ability of the flightcrew to maintain the safe flight and landing of the airplane.

2009-09-07 - We are adopting a new airworthiness directive (AD) for all Boeing Model 737-100, - 200, -200C, -300, -400, and -500 series airplanes. For all airplanes, this AD requires repetitive overhaul of the retract actuator beam of the main landing gear (MLG). For certain airplanes, this AD requires repetitive inspections for damage of the retract actuator beam, and related investigative and corrective actions if necessary. This AD results from reports of broken retract actuator beams of the MLG and the subsequent failure of the MLG to fully retract. We are issuing this AD to detect and correct broken retract actuator beams of the MLG, which could cause damage to the beam arm, hydraulic tubing, and flight control cables. Damage to the flight control cables could result in loss of control of the airplane.

2009-09-06 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 100, -200, -200C, -300, -400, and -500 series airplanes. This AD requires repetitive detailed and high frequency eddy current inspections to detect cracks of the backup intercostals and the upper sill of the forward airstair doorway, and applicable corrective actions. This AD also provides for an optional terminating action, which would eliminate the need for repetitive inspections. This AD results from a report indicating that cracks were found in the backup intercostals and upper sill web of the forward airstair doorway. We are issuing this AD to detect and correct fatigue cracking of the backup intercostals and upper sill web of the forward airstair doorway, which could result in a rapid loss of cabin pressure.

2009-07-11 - The FAA is superseding an existing airworthiness directive (AD), which applies to all Boeing Model 737-300, -400, and -500 series airplanes. That AD currently requires repetitive inspections for discrepancies of the fuselage skin under the dorsal fin assembly, and repairing if necessary. This new AD requires an inspection for any chafing or crack in the fuselage skin and abrasion resistant coating at the dorsal fin landing, an inspection for damage to the dorsal fin seals, attach clip, and seal retainer, and other specified and corrective actions as necessary. The new requirements will end the need for the existing repetitive inspections. This AD results from a report of an 18-inch crack found in the fuselage skin area under the blade seals of the nose cap of the dorsal fin due to previous wear damage, and additional reports of fuselage skin wear. We are issuing this AD to prevent discrepancies of the fuselage skin, which could result in fatigue cracking due to cabin pressurization and consequent rapid in-flight decompression of the airplane fuselage.

2009-02-06 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 300, -400, and -500 series airplanes. This AD requires repetitive high frequency eddy current inspections for cracking of the 1.04-inch nominal diameter wire penetration hole in the frame and frame reinforcement, between stringers S-20 and S-21, on both the left and right sides of the airplane, and related investigative and corrective actions if necessary. This AD results from reports of cracking in the frame, or in the frame and frame reinforcement, common to the 1.04-inch nominal diameter wire penetration hole intended for wire routing. We are issuing this AD to detect and correct cracking in the fuselage frames and frame reinforcements, which could reduce the structural capability of the frames to sustain limit loads, and result in cracking in the fuselage skin and subsequent rapid depressurization of the airplane.

2009-04-15 - The FAA is adopting a new airworthiness directive (AD) for certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD requires repetitive internal eddy current and detailed inspections to detect cracked stringer tie clips; measuring the fastener spacing and the edge margin if applicable, and doing applicable corrective and related investigative actions. As a temporary alternative to doing the actions described previously, this AD requires repetitive external general visual inspections of the skin and lap joints and repetitive external eddy current sliding probe inspections, as applicable, of the lap joints for cracks and evidence of overload resulting from cracked stringer tie clips, and applicable corrective actions if necessary. This AD results from a report of several cracked stringer tie clips. We are issuing this AD to detect and correct multiple adjacent cracked stringer tie clips and damaged skin and frames, which could lead to the skin and frame structure developing cracks and consequent decompression of the airplane.

2009-01-02 - SUMMARY: The FAA is adopting a new airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes. This AD requires a one-time general visual inspection of frames between body station (BS) 360 and BS 907 to determine if certain support brackets of the air conditioning (A/C) outlet extrusions are installed; medium- and high-frequency eddy current inspections for cracking of the frames around the attachment holes of the subject brackets; and repair if necessary. This AD also requires installing new, improved fittings for all support brackets of the A/C outlet extrusions between BS 360 and BS 907. This AD results from numerous reports of multiple cracks in the frames around the attachment holes of certain support brackets of the A/C outlet extrusions. We are issuing this AD to prevent frame cracking, which, if not corrected, could lead to a severed frame that, combined with cracking of the skin lap splice above stringer 10, could result in rapid decompression of the airplane.

2008-24-08 - SUMMARY: We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 600, -700, -700C, -800 and -900 series airplanes. This AD requires an inspection of the escape slides for the forward and aft entry and service doors to determine the part number and service bulletin number stenciled on the escape slide girt, and modification of the escape slide assemblies. This AD also requires concurrent modification of the escape slide latch assemblies; concurrent inspection of the escape slides to determine the part number and service bulletin number stenciled on the escape slide girts, and replacement of the trigger housing on the regulator valve with an improved trigger housing if necessary; and concurrent replacement of the rod in the pilot valve regulator with a new, improved rod; as applicable. This AD results from reports that certain escape slides did not automatically inflate when deployed or after the manual inflation cable was pulled. We are issuing this AD to prevent failure of an escape slide to inflate when deployed, which could result in the slide being unusable during an emergency evacuation and consequent injury to passengers or crewmembers.

2008-24-05 - SUMMARY: We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 400, -500, -600, -700, -700C, -800, and -900 series airplanes. This AD requires an inspection to determine the part and serial numbers of the windshield wiper motors for the pilot's and first officer's windshields, and doing applicable corrective actions. This AD results from two reports that the left and right windshield wipers stopped working in flight. We are issuing this AD to prevent failure of the windshield wipers in wet weather, which could result in decreased visibility for the flightcrew.

2008-24-51-Emergency - BACKGROUND: We received a report of failure of the left-hand fuel pump of the center wing tank (CWT) to shut off after being selected “OFF” by the flightcrew during flight on a Boeing Model 737-700 airplane. Subsequent to that report, the failure was found on two additional airplanes. Information indicates that the autoshutoff system appears to function normally; however, when the flightcrew manually turns off the CWT pump switches, that action turns off the right-hand pump, but re-energizes the left-hand pump due to incorrect wiring. The low-pressure lights turn off, incorrectly indicating to the flightcrew that power to both pumps has been removed. The failure condition results in continual running of the left-hand fuel pump without indication to the flightcrew, which could lead to localized overheating of parts inside the fuel pump, and which could produce an ignition source inside the fuel tank.

Investigation revealed that incorrect wiring could occur on airplanes on which an autoshutoff system was installed in accordance with Boeing Alert Service Bulletin 737-28A1206. Functional tests conducted in accordance with that service bulletin are not adequate to detect the incorrect wiring condition.

We approved installation of the autoshutoff system as an alternative method of compliance to AD 2002-24-51, amendment 39-12992 (68 FR 10, January 2, 2003). That AD was issued to address reports indicating that two fuel tank pumps showed evidence of extreme localized overheating of parts in the priming and vapor pump section of the fuel pump. That AD required revising the airplane flight manual (AFM) to require the flightcrew to maintain certain minimal fuel levels in the center fuel tanks.

2008-13-12-R1 - SUMMARY: The FAA is revising an existing airworthiness directive (AD) that applies to certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. That AD currently requires various repetitive inspections for cracking of the upper frame to side frame splice of the fuselage, and other specified and corrective actions if necessary. That AD also provides for an optional preventive modification, which terminates the repetitive inspections. This new AD adds an optional terminating action that was inadvertently omitted from that AD. This AD results from a report that the upper frame of the fuselage was severed between stringers S-13L and S-14L at station 747, and the adjacent frame at station 767 had a 1.3-inch-long crack at the same stringer location. We are issuing this AD to detect and correct fatigue cracking of the upper frame to side frame splice of the fuselage, which could result in reduced structural integrity of the frame and adjacent lap joint. This reduced structural integrity can increase loading in the fuselage skin, which will accelerate skin crack growth and result in decompression of the airplane.

2008-23-09 - SUMMARY: We are adopting a new airworthiness directive (AD) for certain Boeing transport category airplanes. This AD requires replacing any insulation blanket constructed of polyethyleneteraphthalate (PET) film, ORCON Orcofilm[reg] AN-26 (hereafter ''AN-26''), with a new insulation blanket. This AD results from reports of in-flight and ground fires on certain airplanes manufactured with insulation blankets covered with AN-26, which may contribute to the spread of a fire when ignition occurs from sources such as electrical arcing or sparking. We are issuing this AD to ensure that insulation blankets constructed of AN-26 are removed from the fuselage. Such insulation blankets could ignite and propagate a fire that is the result of electrical arcing or sparking.

2008-23-07 - SUMMARY: We are adopting a new airworthiness directive (AD) for all Boeing Model 737 airplanes. This AD requires revising the airplane flight manual to include a new flightcrew briefing that must be done before the first flight of the day and following any change in flightcrew members, and to advise the flightcrew of this additional briefing. This AD results from continuing reports that flightcrews have failed to recognize and react properly to the cabin altitude warning horn. We are issuing this AD to prevent failure of the flightcrew to recognize and react properly to a valid cabin altitude warning horn, which could result in incapacitation of the flightcrew due to hypoxia (lack of oxygen in body) and consequent loss of airplane control.

2008-22-01 - We are adopting a new airworthiness directive (AD) for various transport category airplanes. This AD requires deactivation of PATS Aircraft, LLC, auxiliary fuel tanks. This AD results from fuel system reviews conducted by the manufacturer, which identified unsafe conditions for which the manufacturer has not provided corrective actions. We are issuing this AD to prevent the potential of ignition sources inside fuel tanks, which, in combination with flammable fuel vapors, could result in fuel tank explosions and consequent loss of the airplane.

2008-17-13 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 100, -200, -200C, -300, -400, and -500 series airplanes. This AD requires replacing the existing straight-to-90-degree hose assembly for the Lavatory ''A'' water supply. The replacement is a new straight hose assembly and a separate 90-degree elbow fitting. This AD results from a report of a separated hose assembly for the passenger water system. We are issuing this AD to prevent a water leak into the flight deck ceiling, which could result in an electrical short and possible loss of several functions essential to safe flight.

2008-19-03 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 300, -400, and -500 series airplanes. This AD requires repetitive external detailed inspections or nondestructive inspections to detect cracks in the fuselage skin along the chem-mill steps at stringers S-1 and S-2R, between station (STA) 400 and STA 460, and repair if necessary. This AD results from reports of cracks in the fuselage skin common to stringer S-1 and between STA 400 and STA 460. We are issuing this AD to detect and correct fatigue cracking of the fuselage skin panels at the chemmill steps, which could result in sudden fracture and failure of the fuselage skin panels, and consequent rapid decompression of the airplane.

2008-17-15 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 600, -700, -800, and -900 series airplanes. This AD requires installing hot short protector (HSP) support brackets and equipment for the fuel quantity indicating system (FQIS) fuel densitometer and other specified actions as applicable. This AD also requires revising the Airworthiness Limitations (AWLs) section of the Instructions for Continued Airworthiness to incorporate AWL No. 28-AWL- 07. This AD results from fuel system reviews conducted by the manufacturer. We are issuing this AD to prevent the center tank fuel densitometer from overheating and becoming a potential ignition source inside the center fuel tank, which, in combination with flammable fuel vapors, could result in a center fuel tank explosion and consequent loss of the airplane.

2008-17-03 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 100, -200, -200C, -300, -400, and -500 series airplanes. This AD requires repetitive inspections to detect cracking of the body station 303.9 frame, and corrective action if necessary. This AD also provides for optional terminating action for the repetitive inspections. This AD results from reports of cracks found at the cutout in the web of body station frame 303.9 inboard of stringer 16L. We are issuing this AD to detect and correct such cracking, which could prevent the left forward entry door from sealing correctly, and could cause in-flight decompression of the airplane.

2008-16-13 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 600, -700, -700C, -800, -900, and -900ER series airplanes. This AD requires replacing the pushrods for the left and right elevator tab control mechanisms with new, improved pushrods. This AD results from a report of a rod end fracture on a rudder power control unit (PCU) control rod, which is similar to the ones used for the elevator tab pushrods. Analysis revealed that the fractured rod end had an incorrect hardness, which had probably occurred during the manufacture of the control rod. We are issuing this AD to prevent fracture of the elevator tab pushrod ends, which could result in excessive in-flight vibrations of the elevator tab, possible loss of the elevator tab, and consequent loss of controllability of the airplane.

2008-15-05 - We are adopting a new airworthiness directive (AD) for all Boeing Model 737-300, - 400, and -500 series airplanes. This AD requires inspecting to determine if certain carriage spindles are installed, repetitive inspections for corrosion and indications of corrosion on affected carriage spindles, and if necessary, related investigative action and corrective action. This AD also provides optional terminating action. This AD results from a report of corrosion found on carriage spindles that are located on the outboard trailing edge flaps. We are issuing this AD to detect and correct corrosion of the carriage spindle, which could result in fracture. Fracture of both the inboard and outboard carriage spindles, in the forward ends through the large diameters, on a flap, could adversely affect the airplane's continued safe flight and landing.

2008-13-25 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 300 and -400 series airplanes. This AD requires testing and inspecting a certain web panel of the main wheel well pressure deck to determine the material type and thickness; and related investigative and corrective actions if necessary. This AD results from several reports indicating that cracks ranging from 0.8 to 8.0 inches long were found on a certain web panel of the main wheel well pressure deck. We are issuing this AD to prevent fatigue cracking in the web panel of the main wheel well pressure deck, which could result in venting and consequent decompression of the airplane.

2008-13-12 - We are adopting a new airworthiness directive (AD) for certain Boeing Model 737- 100, -200, -200C, -300, -400, and -500 series airplanes. This AD requires various repetitive inspections for cracking of the upper frame to side frame splice of the fuselage, and other specified and corrective actions if necessary. This AD also provides for an optional preventive modification, which terminates the repetitive inspections. This AD results from a report that the upper frame of the fuselage was severed between stringers S-13L and S-14L at station 747, and the adjacent frame at station 767 had a 1.3-inch-long crack at the same stringer location. We are issuing this AD to detect and correct fatigue cracking of the upper frame to side frame splice of the fuselage, which could result in reduced structural integrity of the frame and adjacent lap joint. This reduced structural integrity can increase loading in the fuselage skin, which will accelerate skin crack growth and result in decompression of the airplane.

2008-12-04 - We are
adopting a new airworthiness directive (AD) for certain Boeing Model 737- 600,
-700, -700C, -800, and -900 series airplanes. This AD requires various
repetitive inspections to detect cracks along the chemically milled steps of the
fuselage skin or missing or loose fasteners in the area of the preventative
modification or repairs, replacement of the time-limited repair with the
permanent repair if applicable, and applicable corrective actions if necessary,
which would end certain repetitive inspections. This AD results from a fatigue
test that revealed numerous cracks in the upper skin panel at the chemically
milled step above the lap joint. We are issuing this AD to detect and correct
such fatigue-related cracks, which could result in the crack tips continuing to
turn and grow to the point where the skin bay flaps open, causing decompression
of the airplane.

2008-12-03 - We are
adopting a new airworthiness directive (AD) for various transport category
airplanes. This AD requires deactivation of Rogerson Aircraft Corporation
auxiliary fuel tanks. This AD results from fuel system reviews conducted by the
manufacturer, which identified potential unsafe conditions for which the
manufacturer has not provided corrective actions. We are issuing this AD to
prevent the potential of ignition sources inside fuel tanks, which, in
combination with flammable fuel vapors, could result in fuel tank explosions and
consequent loss of the airplane.

2008-11-08 - We are adopting a new
airworthiness directive (AD) for all Boeing Model 737-600, - 700, -700C, -800,
-900, and -900ER series airplanes. This AD requires repetitive inspections for
any cracking of or damage to the left side and right side flight deck No. 2, No.
4, and No. 5 windows, as necessary, and corrective actions if necessary. This AD
results from reports of in-flight departure and separation of the flight deck
windows. We are issuing this AD to detect and correct cracking in the vinyl
interlayer or damage to the structural inner glass panes of the flight deck No.
2, No. 4, and No. 5 windows, which could result in loss of a window and rapid
loss of cabin pressure. Loss of cabin pressure could cause crew communication
difficulties or crew incapacitation.

NM-08-24 - This Special
Airworthiness Information Bulletin alerts you of an airworthiness concern on all
Boeing Model 737 airplanes relating to the potential failure of certain potable
water couplers during freezing weather conditions. The failure of the couplers
could result in water spraying and freezing around the outflow valve, rendering
the valve inoperative. If enough ice forms, the performance of the outflow valve
will be very limited. This could result in difficulty controlling cabin
pressure.

2008-11-04 -
We are adopting a new airworthiness directive (AD) for all Boeing Model
737-100, - 200, -200C, -300, -400, and -500 series airplanes. This AD requires
repetitive inspections for cracking in and around the upper and lower hinge
cutouts of the forward entry and forward galley service doorways, and corrective
actions if necessary. This AD results from multiple reports of cracks found in
the skin, bearstrap, and/or frame outer chord in the hinge cutout areas of the
forward entry and forward galley service doorways. We are issuing this AD to
detect and correct such cracking, which could result in rapid decompression of
the airplane.

2008-11-03 - We are adopting a new
airworthiness directive (AD) for all Boeing Model 737-100, - 200, and -200C
series airplanes. This AD requires revising the FAA-approved maintenance
inspection program to include inspections that will give no less than the
required damage tolerance rating for each structural significant item (SSI),
doing repetitive inspections to detect cracks of all SSIs, and repairing cracked
structure. This AD results from a report of incidents involving fatigue cracking
in transport category airplanes that are approaching or have exceeded their
design service objective. We are issuing this AD to maintain the continued
structural integrity of the entire fleet of Model 737-100, -200, and -200C
series airplanes.

2008-10-10 - We are
adopting a new airworthiness directive (AD) for certain Boeing Model 737- 600,
-700, -700C, -800, and -900 series airplanes. This AD requires revising the
Airworthiness Limitations (AWLs) section of the Instructions for Continued
Airworthiness by incorporating new limitations for fuel tank systems to satisfy
Special Federal Aviation Regulation No. 88 requirements. This AD also requires
the initial inspection of a certain repetitive AWL inspection to phase in that
inspection, and repair if necessary. This AD results from a design review of the
fuel tank systems. We are issuing this AD to prevent the potential for ignition
sources inside fuel tanks caused by latent failures, alterations, repairs, or
maintenance actions, which, in combination with flammable fuel vapors, could
result in a fuel tank explosion and consequent loss of the airplane.

2008-10-09 - We are adopting a new
airworthiness directive (AD) for all Boeing Model 737-100, - 200, -200C, -300,
-400, and -500 series airplanes. This AD requires revising the FAA-approved
maintenance program to incorporate new airworthiness limitations (AWLs) for fuel
tank systems to satisfy Special Federal Aviation Regulation No. 88 requirements.
This AD also requires the initial inspection of a certain repetitive AWL
inspection to phase in that inspection, and repair if necessary. This AD results
from a design review of the fuel tank system. We are issuing this AD to prevent
the potential for ignition sources inside fuel tanks caused by latent failures,
alterations, repairs, or maintenance actions, which, in combination with
flammable fuel vapors, could result in a fuel tank explosion and consequent loss
of the airplane.

2008-09-15 - We are
adopting a new airworthiness directive (AD) for all Boeing Model 737-100, - 200,
-200C, -300, -400, and -500 series airplanes. This AD requires repetitive
inspections for any cracking of or damage to the left side and right side flight
deck No. 2, No. 4, and No. 5 windows and corrective actions if necessary. This
AD results from reports of in-flight departure and separation of the flight deck
windows. We are issuing this AD to detect and correct cracking in the vinyl
interlayer or damage to the structural inner glass panes of the flight deck No.
2, No. 4, and No. 5 windows, which could result in loss of a window and rapid
loss of cabin pressure. Loss of cabin pressure could cause crew communication
difficulties or crew incapacitation.

2008-09-14 - We are adopting a new
airworthiness directive (AD) for certain Boeing Model 737- 600, -700, -700C,
-800 and -900 series airplanes. This AD requires inspecting ground blocks GD261
and GD264 for corrosion, measuring the electrical bond resistance between the
ground blocks and the airplane structure, separating the ground wires for the
fuel boost pump circuit between ground blocks GD261 and GD264, and doing
corrective actions if necessary. This AD results from a report of random flashes
of the six fuel pump low pressure lights and intermittent operation of the fuel
boost pumps. We are issuing this AD to prevent the simultaneous malfunction of
all six fuel boost pumps, which could cause the engines to operate on suction
feed and potentially flame out.

2008-09-13 - We are adopting a new
airworthiness directive (AD) for all Boeing Model 737-300, - 400, and -500
series airplanes. This AD requires revising the FAA-approved maintenance
inspection program to include inspections that will give no less than the
required damage tolerance rating for each structural significant item (SSI),
doing repetitive inspections to detect cracks of all SSIs, and repairing cracked
structure. This AD results from a report of incidents involving fatigue cracking
in transport category airplanes that are approaching or have exceeded their
design service objective. We are issuing this AD to maintain the continued
structural integrity of the entire fleet of Model 737-300, -400, and -500 series
airplanes.

2008-08-24 - We are
adopting a new airworthiness directive (AD) for certain Boeing Model 737- 600,
-700, -700C, -800, and -900 series airplanes. This AD requires replacing the
drain tube assemblies and support clamps on the aft fairing of the engine
struts. This AD results from reports of failure of the drain tube assembly and
clamp on the aft fairings of an engine strut. We are issuing this AD to prevent
failure of the drain tube assemblies and clamps on the aft fairings of the of
the engine struts. Such a failure could allow leaked flammable fluids in the
drain systems to discharge on to the heat shields of the aft fairings of the
engine struts, which could result in an undetected and uncontrollable fire.

2008-08-23 - We are adopting a new
airworthiness directive (AD) for all Boeing Model 737-200C series airplanes.
This AD requires revising the FAA-approved maintenance inspection program to
include inspections that will give no less than the required damage tolerance
rating for each structural significant item (SSI), doing repetitive inspections
to detect cracks of all SSIs, and repairing cracked structure. This AD results
from a report of incidents involving fatigue cracking in transport category
airplanes that are approaching or have exceeded their design service objective.
We are issuing this AD to maintain the continued structural integrity of the
entire fleet of Model 737-200C series airplanes.

2008-08-22 - We are adopting a new
airworthiness directive (AD) for certain Boeing Model 737- 600, -700, -700C,
-800, and -900 series airplanes. This AD requires a one-time inspection to
determine the material of the forward and aft gray water drain masts. For
airplanes having composite gray water drain masts, this AD requires installation
of a bonding jumper between a ground and the clamp on the tube of the forward
and aft gray water composite drain masts. This AD results from a report of
charred insulation blankets and burned wires around the forward gray water
composite drain mast found during an inspection of the forward cargo compartment
on a Model 767-300F airplane. We are issuing this AD to prevent a fire near a
composite drain mast and possible disruption of the electrical power system
caused by a lightning strike on a composite drain mast, which could result in
the loss of several functions essential for safe flight.

2008-08-10 - We are
adopting a new airworthiness directive (AD) for all Boeing Model 737-100, - 200,
-200C, -300, -400, and -500 series airplanes. For certain airplanes, this AD
requires replacing the outboard stabilizing fitting and certain adjacent
components of the main landing gear (MLG) support beam. This AD also requires
repetitive inspections for discrepancies of the outboard stabilizing fitting,
walking beam hanger, and rear spar attachment, and corrective actions if
necessary. For certain airplanes, this AD provides an alternative one-time
inspection of the outboard stabilizing fitting for discrepancies, and corrective
actions if necessary, which would extend the compliance time for the replacement
of the outboard stabilizing fitting. For certain other airplanes, this AD also
requires performing a torque check of the aft pin of the outboard stabilizing
fitting, and corrective actions if necessary. This AD results from reports of
findings of fatigue cracking of the outboard stabilizing fitting and stress
corrosion cracking of the bolts attaching the fitting to the wing rear spar. We
are issuing this AD to detect and correct that cracking, which could result in
disconnection of the MLG actuator from the rear spar and support beam,
consequent damage to the hydraulic system, and possible loss of the ''A'' and
''B'' hydraulic systems and damage or jamming of the flight control cables.
Damage or jamming of the flight control cables could result in loss of control
of the airplane.

2008-06-29 - We are
adopting a new airworthiness directive (AD) for all Boeing Model 737-300, - 400,
and -500 series airplanes. This AD requires repetitive inspections of the
downstop assemblies on the main tracks of the No. 2, 3, 4, and 5 slats and the
inboard track of the No. 1 and 6 slats to verify if any parts are missing,
damaged, or in the wrong order. This AD also requires other specified actions,
and related investigative and corrective actions if necessary. This AD results
from reports of fuel leaking from a puncture in the slat track housing (referred
to as the ''slat can''). We are issuing this AD to detect and correct loose or
missing parts from the main slat track downstop assemblies, which could puncture
the slat can and result in a fuel leak and consequent fire.

2008-06-24 - We are
adopting a new airworthiness directive (AD) for certain Boeing Model 737- 300,
-400, and -500 series airplanes. This AD requires an inspection to determine the
manufacturer and manufacture date of the oxygen masks in the passenger service
unit and the lavatory and attendant box assemblies, corrective action if
necessary, and other specified action. This AD results from a report that
several passenger masks with broken in-line flow indicators were found following
a mask deployment. We are issuing this AD to prevent the in-line flow indicators
of the passenger oxygen masks from fracturing and separating, which could
inhibit oxygen flow to the masks and consequently result in exposure of the
passengers and cabin attendants to hypoxia following a depressurization event.

2008-06-09 -
We are adopting a new airworthiness directive (AD) for certain Boeing Model 737-
200 series airplanes. This AD requires repetitive inspections to detect cracking
of the support fittings of the Krueger flap actuators, and corrective actions if
necessary. This AD also requires eventual replacement of any existing aluminum
support fitting on each wing with a steel fitting, and modification of the aft
attachment of the actuator. Doing these actions terminates the repetitive
inspection requirements. This AD results from reports of cracking due to fatigue
and stress corrosion of the support fittings of the Krueger flap actuator. We
are issuing this AD to prevent cracking of the support fittings, which could
result in fracturing of the actuator attach lugs, separation of the actuator
from the support fitting, severing of the hydraulic lines, resultant loss of
hydraulic fluids, and consequent reduced controllability of the airplane.

2008-06-03 - The FAA is adopting a new
airworthiness directive (AD) for certain Boeing airplanes, identified above.
This AD requires inspecting to determine if certain motor-operated shutoff valve
actuators for the fuel tanks are installed, and related investigative and
corrective actions if necessary. This AD also requires revising the
Airworthiness Limitations (AWLs) section of the Instructions for Continued
Airworthiness to incorporate AWL No. 28-AWL-21, No. 28-AWL-22, and No. 28-AWL-
24 (for Model 737-600, -700, -700C, -800 and -900 series airplanes); and No.
28-AWL-23, No. 28- AWL-24, and No. 28-AWL-25 (for Model 757-200, -200PF, -200CB,
and -300 series airplanes). This AD results from a design review of the fuel
tank systems. We are issuing this AD to prevent electrical energy from
lightning, hot shorts, or fault current from entering the fuel tank through the
actuator shaft, which could result in fuel tank explosions and consequent loss
of the airplane.

2008-05-06 - We are adopting a new
airworthiness directive (AD) for certain Boeing Model 737- 100, -200, -300,
-400, and -500 series airplanes. This AD requires repetitive inspections for
fatigue cracking in the longitudinal floor beam web, upper chord, and lower
chord located at certain body stations, and repair if necessary. This AD results
from several reports of cracks in the center wing box longitudinal floor beams,
upper chord, and lower chord. We are issuing this AD to detect and correct
fatigue cracking of the upper and lower chords and web of the longitudinal floor
beams, which could result in rapid loss of cabin pressure.

2008-05-05 - We are adopting a new
airworthiness directive (AD) for certain Boeing Model 737- 600, 737-700,
737-700C, 737-800, and 737-900 series airplanes. This AD requires an inspection
of the vertical fin lugs, skin, and skin edges for discrepancies; an inspection
of the flight control cables, fittings, and pulleys in section 48 for signs of
corrosion; an inspection of the horizontal stabilizer jackscrew, ball nut, and
gimbal pins for signs of corrosion; and corrective actions if necessary. This AD
results from reports indicating that moisture was found within the section 48
cavity. We are issuing this AD to ensure that the correct amount of sealant was
applied around the vertical fin lugs, skin and the skin edges. Missing sealant
could result in icing of the elevator cables, which could cause a system jam and
corrosion of structural and flight control parts, resulting in reduced
controllability of the airplane.

2008-04-21 - We are adopting a new
airworthiness directive (AD) for certain Boeing Model 737- 300, -400, and -500
series airplanes. This AD requires repetitive inspections for cracking of the
body buttock line (BBL) 0.07 floor beam between body station (BS) 651 and BS 676
and between BS 698 and BS 717, and related investigative and corrective actions
if necessary. This AD also provides an optional terminating action for the
repetitive inspections. This AD results from reports of cracking in the BBL 0.07
floor beam. We are issuing this AD to prevent failure of the main deck floor
beams at certain body stations due to fatigue cracking, which could result in
rapid decompression of the airplane.

2008-03-20 - The FAA is adopting a new
airworthiness directive (AD) for certain Boeing Model 737-300, -400, and -500
series airplanes. This AD requires, among other actions, modifying the
doormounted escape system of the forward right side door slide compartment. This
AD results from reports indicating that the forward right escape slide inflated
90 degrees out of alignment after deployment from the forward right side slide
compartment. We are issuing this AD to prevent the escape slide from being
unusable during an emergency evacuation and consequent injury to passengers or
crewmembers.

2007-26-04 - We are adopting a new
airworthiness directive (AD) for certain Boeing Model 737- 100, -200, -200C,
-300, -400, and -500 series airplanes. This AD requires repetitive detailed and
high-frequency eddy current inspections for cracking around the heads of the
fasteners on the forward fastener row of certain areas of the station (STA)
259.5 circumferential butt splice, and repair if necessary. This AD also
requires a preventive modification, which eliminates the need for the repetitive
inspections. This AD results from a report that an operator found multiple
cracks in the fuselage skin of a Model 737-200 airplane, at the forward fastener
row of the STA 259.5 circumferential butt splice between stringers 19 and 24. We
are issuing this AD to prevent cracking of the STA 259.5 circumferential butt
splice, which could result in loss of structural integrity of the fuselage skin
and possible loss of cabin pressure.

2007-25-03 - The FAA is adopting a new
airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C,
-800, and -900 series airplanes. This AD requires repetitive inspections of
either the aft side or forward side of the aft pressure bulkhead for oil can
conditions or bulges, a onetime inspection of the aft pressure bulkhead to
identify any previously installed web repair, and corrective actions if
necessary. This AD results from web oil can conditions found on the aft pressure
bulkhead of several airplanes. We are issuing this AD to detect and correct oil
can conditions, bulges, or previous repairs in the aft pressure bulkhead, which
could lead to web cracks and consequently result in rapid decompression of the
airplane.

2007-24-02 - The FAA is superseding an
existing airworthiness directive (AD) that applies to all Model 737-100, -200,
-200C, -300, -400, and -500 series airplanes. The existing AD currently requires
repetitive detailed inspections for damage of the electrical wire and sleeve
that run to the fuel boost pump through a conduit in the fuel tank, and arcing
damage of the conduit and signs of fuel leakage into the conduit; replacement of
the sleeve with a new, smaller-diameter sleeve; and related investigative and
corrective actions, as applicable. This new AD reduces the inspection threshold
for certain airplanes. This AD results from a report of a fuel tank explosion on
a Model 727-200F airplane on the ground, and a report of chafed wires and a
damaged power cable sleeve of a fuel boost pump discovered during an inspection
on a Model 737-300 airplane. (The fuel boost pump installation on certain Model
737 airplanes is almost identical to the installation on Model 727 airplanes.)
We are issuing this AD to detect and correct chafing of the fuel boost pump
electrical wiring and leakage of fuel into the conduit, and to prevent
electrical arcing between the wiring and the surrounding conduit, which could
result in arc-through of the conduit, and consequent fire or explosion of the
fuel tank.

NM-07-47 - This Special Airworthiness Information
Bulletin (SAIB) advises you, owners and operators of Boeing Model 737 series
airplanes equipped with forward airstairs, of a potential personal injury risk
associated with the possibility for small children to fall through openings in
the airstair handrails.

2007-18-52 - This document publishes in the
Federal Register an amendment adopting airworthiness directive (AD) 2007-18-52
that was sent previously to all known U.S. owners and operators of Boeing Model
737-600, -700, -700C, -800, -900, and -900ER series airplanes by individual
notices. This AD requires repetitive detailed inspections of the slat track
downstop assemblies to verify that proper hardware is installed, one-time
torquing of the nut and bolt, and corrective actions if necessary. This AD is
prompted by reports of parts coming off the main slat track downstop assemblies.
We are issuing this AD to detect and correct loose or missing parts from the
main slat track downstop assemblies, which could result in a fuel leak and
consequent fire.

2007-18-51 - We have received reports of
parts of the main slat track downstop assembly coming off the main slat track.
In one case, a nut fell into the slat track housing (referred to as “slat can”)
and, during a subsequent slat retraction, the track made contact with the nut,
pushing it into the wall of the can and puncturing it. That operator reported
finding fuel leaking from the drain hole in the slat track housing at the No. 5
slat track position. In another case, an initial investigation revealed that
following retraction of the slats after landing on a Model 737-800 airplane,
loose parts of the main slat track downstop assembly punctured the slat can,
which resulted in a fuel leak and a fire that ultimately destroyed the airplane.
Loose or missing parts from the main slat track downstop assemblies, if not
detected and corrected, could result in a fuel leak and consequent fire.

2007-15-04 - The FAA is superseding an
existing airworthiness directive (AD) that applies to certain Boeing Model
737-800 series airplanes. The existing AD currently requires inspecting flight
spoilers to determine spoiler position after every landing and after any
rejected takeoff maneuver. For airplanes on which any flight spoiler is found in
the up position with the speedbrake handle in the down position, the existing AD
requires replacing the flight spoiler actuator with a flight spoiler actuator
having a certain part number. The existing AD also requires an operational test
of the speedbrake control system after any maintenance actions that operate the
spoiler system, and replacement of the flight spoiler actuator if necessary. The
existing AD also provides for optional terminating action for those
requirements. This new AD requires the previously optional terminating action.
This AD results from a report of seven flight spoiler actuator jams on Model
737-800 airplanes equipped for short field performance (SFP). The cause of the
failure has been identified as interference within the actuator main control
valve. We are issuing this AD to prevent operation with defective flight spoiler
actuators, which could result in a flight spoiler actuator hardover, and could
cause the flight spoiler surface to jam in the fully extended position. Two or
more hardover failures of the flight spoiler surfaces in the up direction on the
same wing, if undetected prior to takeoff, can cause significant roll and
consequent loss of control of the airplane.